trio

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Music A composition for three voices or three instruments.
2. n. Music A group of three singers or three instrumentalists.
3. n. Music The middle, contrasting section of a minuet, scherzo, march, or various other forms.
4. n. A group of three.

Century Dictionary and Cyclopedia

1. n. In music, a composition or movement for three solo parts, either vocal or instrumental, usually without accompaniment. Specifically, either
2. n. A company of three vocalists or instrumentalists who perform trios.
3. n. A group, combination, or association of three.
4. n. In the game of piquet, three aces, kings, queens, or knaves, held in one hand: a counting combination of cards.

Wiktionary

1. n. A group of three people or things.
2. n. A group of three musicians.
3. n. music A piece of music written for three musicians.
4. n. music A passage in the middle of a minuet, frequently in a different key.
5. n. Any cocktail made with a spirit, a liqueur, and a creamy ingredient.

GNU Webster's 1913

1. n. Three, considered collectively; three in company or acting together; a set of three; three united.
2. n. A composition for three parts or three instruments.
3. n. The secondary, or episodical, movement of a minuet or scherzo, as in a sonata or symphony, or of a march, or of various dance forms; -- not limited to three parts or instruments.

WordNet 3.0

1. n. the cardinal number that is the sum of one and one and one
2. n. three performers or singers who perform together
3. n. a musical composition for three performers
4. n. a set of three similar things considered as a unit
5. n. three people considered as a unit