but

American Heritage® Dictionary of the English Language, Fourth Edition

1. conj. On the contrary: the plan caused not prosperity but ruin.
2. conj. Contrary to expectation; yet: She organized her work but accomplished very little. He is tired but happy.
3. conj. Usage Problem Used to indicate an exception: No one but she saw the prowler.
4. conj. With the exception that; except that. Often used with that: would have joined the band but he couldn't spare the time; would have resisted but that they lacked courage.
5. conj. Informal Without the result that: It never rains but it pours.
6. conj. Informal That. Often used after a negative: There is no doubt but right will prevail.
7. conj. That . . . not. Used after a negative or question: There never is a tax law presented but someone will oppose it.
8. conj. If not; unless: "Ten to one but the police have got them” ( Charlotte M. Yonge).
9. conj. Informal Than: They had no sooner arrived but they turned around and left.
10. prep. Usage Problem Except.
11. adv. Merely; just; only: hopes that lasted but a moment.
12. adv. Used as an intensive: Get out of here but fast!
13. idiom. but for Were it not for: except for: We would have reached the summit but for the weather.

Century Dictionary and Cyclopedia

1. Outside; without; out.
2. In or to the outer room of a cottage having a but and a ben: as, he was but a few minutes ago; he gaed but just now.
3. Only; merely; just. See III.
4. Outside of; without.—
5. To the outside of.—
6. To the outer apartment of: as, gae but the house.
7. Without; not having; apart from.
8. Except; besides; more than. [In this use generally preceded by a clause containing or implying a negation, and not easily separable from the conjunctional use, under which most of the examples fall. The conjunction, on the other hand, in some elliptical constructions assumes a prepositional phase, and in other constructions an adverbial phase. See below.]
9. Except; unless: after a clause containing or implying a negation, and introducing the following clause, in which (the verb being usually omitted because implied in the preceding clause) but before the noun (subject or object of the omitted verb) comes to be regarded as a preposition governing the noun.
10. The clause introduced by but (the apparent object of the qnasi-preposition) may be a single word, an infinitive or prepositional phrase, or a clause with that.
11. By ellipsis of the subject of the clause introduced by but in this construction, but becomes equivalent to that … not or who … not.
12. In this construction the negative, being implied in but, came to be omitted, especially in connection with the verbbe, in the principal clause, the construction “There is not but one God,” as in the first example, becoming “There is but one God,” leaving but as a quasi-adverb, ‘only, merely, simply.’ This use is also extended to constructions not originally negative.
13. To the last two constructions, respectively, belong the idioms “I cannot but hope that,” etc., and “I can but hope that,” etc. The former has suffered ellipsis of the principal verb in the first clause: “I cannot do anything but hope,” or “anything else than hope,” or “otherwise than hope,” etc., implying constraint, in that there is an alternative which one is mentally unable or reluctant to accept, but being equivalent to otherwise than. The latter, “I can but hope that,” etc., has suffered further ellipsis of the negative, and, though historically the same as the former, is idiomatically different: “I can only hope that,” etc., implying restraint, in that there is no alternative or opportunity of action, but being equivalent to only, not otherwise than, or no more than.
14. In an interrogative sentence implying a negative answer, can but is equivalent to cannot but in a declarative sentence.
15. After doubt, or doubt not, and other expressions involving a negative, but may be used as after other negatives, but that being often used pleonastically for that.
16. Hence the use of but with if or that, forming a unitary phrase but if, ‘unless, if not,’ but that, ‘except that, unless’ (these phrases having of course also their analytical meaning, with but in its adversative use).
17. The phrase but that, often abbreviated to but, thus takes an extended meaning. If not; unless.
18. Escept that, otherwise than that, that … not. After negative clauses.
19. The negative clause is often represented by the single word not.
20. An expletive what sometimes, but incorrectly, follows.
21. After interrogative clauses implying a negative answer.
22. After imperative or exclamatory clauses.
23. Excepting or excluding the fact that; save that; were it not that; unless.
24. However; yet; still; nevertheless; notwithstanding: introducing a statement in restriction or modification of the preceding statement.
25. On the contrary; on the other hand: the regular adversative conjunction, introducing a clause in contrast with the preceding.
26. The statement with which the clause with but is thus contrasted may be unexpressed, being implied in the context or supplied by the circumstances.
27. Sometimes, instead of the statement with which the clause with but is contrasted, an exclamation of surprise, admiration, or other strong feeling precedes, the clause with but then expressing the ground of the feeling.
28. Than: after comparatives. [This construction, once in good use, and still common, is now regarded as incorrect.]
29. When. [This use arises out of the comparative construction, “not far, but …,” being equivalent to “not much further than …” See 4.]
30. [By further ellipsis and idiomatic deflection but has in modern English developed a great variety of special and isolated uses derived from the preceding.] Synonyms However, Still, Nevertheless, etc. See however.
31. n. The outer room of a house consisting of only two rooms; the kitchen: the other room being the ben.
32. n. A flounder or plaice.
33. See butt.
34. See butt.
35. Short for abut. See butt.
36. n. See butt.

Wiktionary

1. prep. Outside of.
2. prep. Without, apart from, except.
3. adv. Merely, only.
4. conj. Except (for), excluding.
5. conj. On the contrary, but rather (introducing a word or clause that contrasts with or contradicts the preceding clause or sentence without the not).
6. conj. However, although, nevertheless (implies that the following clause is contrary to prior belief or contrasts with or contradicts the preceding clause or sentence).
7. conj. Without it also happening that; unless that (introducing a necessary concomitant).
8. n. An instance or example of using the word "but"
9. n. The outer room of a small two-room cottage.

GNU Webster's 1913

1. adv. Except with; unless with; without.
2. adv. Except; besides; save.
3. adv. Excepting or excluding the fact that; save that; were it not that; unless; -- elliptical, for but that.
4. adv. Otherwise than that; that not; -- commonly, after a negative, with that.
5. adv. Only; solely; merely.
6. adv. On the contrary; on the other hand; only; yet; still; however; nevertheless; more; further; -- as connective of sentences or clauses of a sentence, in a sense more or less exceptive or adversative.
7. n. The outer apartment or kitchen of a two-roomed house; -- opposed to ben, the inner room.
8. n. A limit; a boundary.
9. n. The end; esp. the larger or thicker end, or the blunt, in distinction from the sharp, end. Now disused in this sense, being replaced by butt{2}. See 1st Butt.
10. v. See butt, v., and abut, v.

WordNet 3.0

1. adv. and nothing more