Pronunciation: (on'set", ôn'-), [key]
1. a beginning or start: the onset of winter.
2. an assault or attack: an onset of the enemy.
3. Phonet.the segment of a syllable preceding the nucleus, as the gr in great. Cf. coda (def. 5), core (def. 14).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.