symphony

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An extended piece in three or more movements for symphony orchestra.
• noun An instrumental passage in a vocal or choral composition.
• noun An instrumental overture or interlude, as in early opera.
• noun A symphony orchestra.
• noun An orchestral concert.
• noun Harmony, especially of sound or color.
• noun Something characterized by a harmonious combination of elements.

from The Century Dictionary.

• noun A consonance or harmony of sounds agreeable to the ear, whether the sounds are vocal or instrumental, or both.
• noun In music: Same as symphonia, 2.
• noun Same as ritornelle.
• noun An elaborate composition in three or more movements, essentially similar in construction to a sonata, but written for an orchestra, and usually of far grander proportions and more varied elements.

from the GNU version of the Collaborative International Dictionary of English.

• noun A consonance or harmony of sounds, agreeable to the ear, whether the sounds are vocal or instrumental, or both.
• noun A stringed instrument formerly in use, somewhat resembling the virginal.
• noun An elaborate instrumental composition for a full orchestra, consisting usually, like the sonata, of three or four contrasted yet inwardly related movements, as the allegro, the adagio, the minuet and trio, or scherzo, and the finale in quick time. The term has recently been applied to large orchestral works in freer form, with arguments or programmes to explain their meaning, such as the “symphonic poems” of Liszt. The term was formerly applied to any composition for an orchestra, as overtures, etc., and still earlier, to certain compositions partly vocal, partly instrumental.
• noun An instrumental passage at the beginning or end, or in the course of, a vocal composition; a prelude, interlude, or postude; a ritornello.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun an extended piece of music of sophisticated structure, usually for orchestra
• noun harmony in music or colour, or a harmonious combination of elements

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a large orchestra; can perform symphonies
• noun a long and complex sonata for symphony orchestra