onset

1 the act or action of setting upon with force or violence the walls withstood the onset of the first battalion Synonyms aggression, assault, attempt, blitz, blitzkrieg, charge, coup de main, descent, offense (or offence), offensive, attack, onslaught, raid, rush, strikeRelated Words ambuscade, ambush; counteraggression, counterassault, counterattack, counteroffensive, counterstrike; sally, sortie; envelopment, flanking; breakthrough, foray, incursion, invasion; pillage, ravage, sack; air raid, bombardment, bombing; siege, storm; barrage, cannonade, fusillade, hail, salvo, volley; whammyNear Antonyms defense, defensive, guard, shield; opposition, resistance; protection, security, shelter

2 the point at which something begins the claim that if you take enough vitamin C at the onset of a cold, you'll often recover faster Synonyms alpha, baseline, birth, commencement, dawn, day one, genesis, get-go (also git-go), inception, incipience, incipiency, kickoff, launch, morning, nascence, nascency, beginning, outset, start, thresholdRelated Words drawing board, first base, ground zero, square one; creation, founding, inauguration, initiation, institution, origination; cradle, fountain, fountainhead, germ, origin, root, seedbed, source, spring, well, wellspring; dawning, opening; advent, appearance, arrival, debut (also début), emergence; childhood, infancy, youthNear Antonyms cessation, closing, closure, completion, finale, finish, period, stop, termination, windupAntonyms close, conclusion, end, ending, omega