See onset in Webster's New World Roget's A-Z Thesaurus II
noun
The act of attacking:
aggression, assailment, assault, attack, attempt, offense, offensive, onrush, onslaught, strike. See attackThe initial stage of a developmental process:
beginning, birth, commencement, dawn, genesis, inception, nascence, nascency, opening, origin, outset, spring, start. See start
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