twin

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One of two offspring born at the same birth.
2. n. One of two identical or similar people, animals, or things; a counterpart.
3. n. Mineralogy Two interwoven crystals that are mirror images of each other.
4. n. A twin-size bed.
5. adj. Being two or one of two offspring born at the same birth: twin sisters.
6. adj. Being two or one of two identical or similar people, animals, or things: twin cities; a twin bed.
7. adj. Botany Of or relating to structures, such as flowers, that occur in pairs.
8. adj. Consisting of two identical or similar parts: a twin lamp fixture.
9. v. To give birth to twins.
10. v. Archaic To be one of twin offspring.
11. v. To be paired or coupled.
12. v. To pair or couple.
13. v. To provide a match or counterpart to.

Century Dictionary and Cyclopedia

1. To cut or form in pairs by cutters or chisels.
2. Two; twain.
3. Consisting of two separate, closely related, and equal members; twofold; double; specifically, consisting of or forming twins or a pair: as, twin children.
4. One, each, or either of two; one of a pair, specifically of two born at a birth: as, a twin brother or sister.
5. In botany, growing in pairs; didymous.
6. Consisting of two chief parts alike, or nearly alike, and held firmly together: as, a twin bottle; a twin vase. The plural is used in the same sense: as, twin vases.
7. In entomology, geminate: applied to spots, punctures, spines, etc., which are close together in pairs, and distant from others.
8. n. Two; twain; a pair; a couple.
9. n. One of two; one of a pair or couple linked together by a particular tie or relation; the mate, counterpart, or fellow of another; specifically, one of two creatures produced at a birth: said of the young both of hitman beings and of beasts.
10. n. A compound crystal one part of which is in a reversed position with reference to the other, as if it had been revolved through 180° about an axis (twinning-axis) perpendicular to a plane which is called the twinning-plane, and is usually a fundamental plane of the given Crystal. Thus if (fig. 1) one half of the octahedron as indicated is revolved through 180° about a vertical axis, the twinned octahedron of fig. 2 results, the twinning-plane being here a face of the octahedron; such twins are common with spinel, and are hence called spinel twins. This is also called a juxtaposition- or contact-tu in, in distinction from a penetration-twin, such as is represented in fig. 3, where each crystal is complete and interpenetrates the other. If the molecular reversal is often repeated in the growth of a crystal, a poly-synthetic twin may result, consisting of successive thin layers or lamellæ of two sets, alternately in reversed position to each other. This is common among the plagioclase feldspars, and is the cause of the fine striatiou often observed on a cleavage-surface. (See albite twin and pericline twin, below.) When the angle between the axes of the two parts of the twin crystal is an aliquot part of 360°, repeated twinning may occur (thus, 3 × 120°, 4 × 90°, 5 × 72°, etc., complete the form); the resulting compound crystal may then imitate (mimetic form) a form of higher symmetry than belongs to the sin*gle crystal, and hence be a case of pseudosymmetry: for example, the twins of aragonite (which has a prismatic angle not far from 120°) have often the form of a pseudo-hexagonal crystal; the six-rayed stellate twins of cerusite give another common example of a repeated twin. In some cases the imitation is so perfect that the true nature of the form can he determined only by an investigation in polarized light.
11. To couple; pair; mate; join intimately or link together; said of two united or of one joined to another.
12. Specifically, in mineralogy, to form or unite into a compound or twin crystal by a reversal of the molecular structure according to some definite law.
13. To be coupled or paired; be mated, as one with another; specifically, to be twin-born.
14. To bring forth two at a birth.
15. To be parted in twain; be divided or sundered; come apart.
16. To part; depart; go away.
17. To be separated (from) or deprived (of): as, to twin with one's gear.
18. To part in twain; sever; sunder.
19. To part, as from another person or thing; separate; sunder; especially, to deprive.

Wiktionary

1. n. Either of two people (or, less commonly, animals) who shared the same uterus at the same time; one who was born at the same birth as a sibling.
2. n. Either of two similar or closely related objects, entities etc.
3. n. A room in a hotel, guesthouse, etc. with two beds; a twin room.
4. n. US A twin size mattress or a bed designed for such a mattress.
5. n. A twin crystal.
6. n. Forming a pair of twins.
7. n. Forming a matched pair.
8. v. transitive, Scotland To separate, divide.
9. v. intransitive, Scotland To split, part; to go away, depart.
10. v. To join, unite; to form links between (now especially of two places in different countries).
11. v. intransitive To give birth to twins.

GNU Webster's 1913

1. adj. Being one of two born at a birth.
2. adj. Being one of a pair much resembling one another; standing in the relation of a twin to something else; -- often followed by to or with.
3. adj. (Bot.) Double; consisting of two similar and corresponding parts.
4. adj. (Crystallog.) Composed of parts united according to some definite law of twinning. See Twin, n., 4.
5. n. One of two produced at a birth, especially by an animal that ordinarily brings forth but one at a birth; -- used chiefly in the plural, and applied to the young of beasts as well as to human young.
6. n. (Astron.) A sign and constellation of the zodiac; Gemini. See Gemini.
7. n. A person or thing that closely resembles another.
8. n. (Crystallog.) A compound crystal composed of two or more crystals, or parts of crystals, in reversed position with reference to each other.
9. v. To bring forth twins.
10. v. To be born at the same birth.
11. v. To cause to be twins, or like twins in any way.
12. v. obsolete To separate into two parts; to part; to divide; hence, to remove; also, to strip; to rob.
13. v. obsolete To depart from a place or thing.

WordNet 3.0

1. v. bring two objects, ideas, or people together
2. n. a waterfall in the Snake River in southern Idaho
3. n. a duplicate copy
4. adj. being two identical
5. v. give birth to twins
6. v. grow as twins
7. n. either of two offspring born at the same time from the same pregnancy
8. n. (astrology) a person who is born while the sun is in Gemini
9. v. duplicate or match