what

American Heritage® Dictionary of the English Language, Fourth Edition

1. pro. Which thing or which particular one of many: What are you having for dinner? What did she say?
2. pro. Which kind, character, or designation: What are these objects?
3. pro. One of how much value or significance: What are possessions to a dying man?
4. pro. That which; the thing that: Listen to what I tell you.
5. pro. Whatever thing that: come what may.
6. pro. Informal Something: I'll tell you what.
7. pro. Nonstandard Which, who, or that: It's the poor what gets the blame.
8. adj. Which one or ones of several or many: What college are you attending? You should know what musical that song is from.
9. adj. Whatever: They soon repaired what damage had been done.
10. adj. How great; how astonishing: What a fool!
11. adv. How much; in what respect; how: What does it matter?
12. conj. That: I don't know but what I'll go.
13. interj. Used to express surprise, incredulity, or other strong and sudden excitement.
14. interj. Chiefly British Used as a tag question, often to solicit agreement.
15. idiom. what for Informal A scolding or strong reprimand: The teacher gave the tardy student what for.
16. idiom. what have you What remains and need not be mentioned: a room full of chairs, lamps, radios, and what have you.
17. idiom. what if What would occur if; suppose that.
18. idiom. what if What does it matter if.
19. idiom. what it takes The necessary expertise or qualities needed for success: She has what it takes to be a doctor.
20. idiom. what's what Informal The fundamentals and details of a situation or process; the true state or condition.
21. idiom. what with Taking into consideration; because of: "I've often wondered why some good crime writer . . . hasn't taken up with New Orleans, what with its special raffishness, its peculiar flavor of bonhomie and a slightly suspect charm” ( Walker Percy).

Century Dictionary and Cyclopedia

1. Used absolutely as an interrogative pronoun. Applied to inanimate things.
2. Applied to animals (and sometimes in contempt to persons) with the force of inquiry after the nature or kind: as, what is that running up the tree?
3. Applied to persons: nearly equivalent to who, but having reference to origin or character, rather than to name or identity.
4. Used in various elliptical and incomplete constructions: as, what? equivalent to what did you say? or what is it?
5. Used in exclamation, to express surprise, indignation, etc.
6. Expressing a summons.
7. A general introductory notion, equivalent to ‘well,’ ‘lo,’ ‘now,’ etc., and constituting a mere expletive.
8. Used adjectively and lending an interrogative force to the proposition in which it occurs. Inquiring as to the individual being, character, kind, or sort of a definite thing or person.
9. Inquiring as to extent or quantity: equivalent to the question how much?
10. Used intensively or emphatically with a force varying from the interrogative to the exclamatory: often followed by the indefinite article: as, what an idea!
11. Elliptical for what say or think you of?
12. A compound relative pronoun, meaning ‘that which,’ or having a value including the simple relative pronoun which with the demonstrative pronoun that preceding: as, “what I have written I have written” (that is, that which I have written I have written). It is no longer used of persons, except in the anomalous phrase but what.
13. What was formerly and in vulgar speech is still used as a simple relative, equivalent to that or which: as, if I had a donkey what wouldn't go.
14. What has also the value of whatever or whoever: as, come what will, I shall be there.
15. Used adjectively, meaning ‘that … which,’ or having compound relative value: as, I know what book you mean (that is, I know that book which you mean); he makes the most of what money he has (that is, he makes the most of that money which he has): applied to persons and things. That … who or which; those … who or which.
16. What sort of; such … as.
17. Any who or which; whatever; whoever.
18. How much.
19. Something; anything: obsolete except in such colloquial phrases as I'll tell you what (by abbreviation for what it is, what I think, or the like).
20. A thing; a portion; an amount; a bit: as, a little what.
21. Why.
22. To what degree? in what respect?
23. How; how greatly; to what an extent or degree; how remarkably: exclamatory and intensive.
24. With omission of the second what (so frequently):
25. So much as; so far as.
26. That. In alwhat, until (compare although, etc.).
27. In the phrase but what: but that; that … not.
28. Quick; sharp; bold.

Wiktionary

1. pro. which thing, event, circumstance, etc.: used interrogatively in asking for the specification of an identity, quantity, quality, etc.
2. pro. An interrogative which asks "Don't you agree?"
3. pro. that; which
4. pro. that which; those that; the thing that
5. adv. in some manner or degree; in part; partly; usually followed by with.
6. adv. Such; this is; that is.
7. adv. Why.
8. adv. Used to introduce each of two coordinate phrases or concepts; both...and.
9. interj. an expression of surprise or disbelief.
10. interj. is that not true?
11. interj. greeting (archaic).
12. which; which kind of.
13. how much; how great (used in an exclamation)

GNU Webster's 1913

1. As an interrogative pronoun, used in asking questions regarding either persons or things
2. As an exclamatory word: -- (a) Used absolutely or independently; -- often with a question following.
3. Used adjectively, meaning how remarkable, or how great
4. Sometimes prefixed to adjectives in an adverbial sense, as nearly equivalent to how
5. As a relative pronoun.
6. Used substantively with the antecedent suppressed, equivalent to that which, or those [persons] who, or those [things] which; -- called a compound relative.
7. Used adjectively, equivalent to the … which; the sort or kind of … which; rarely, the … on, or at, which.
8. Used adverbially in a sense corresponding to the adjectival use.
9. Whatever; whatsoever; what thing soever; -- used indefinitely.
10. Used adverbially, in part; partly; somewhat; -- with a following preposition, especially, with, and commonly with repetition.
11. n. Something; thing; stuff.
12. Why? For what purpose? On what account?