I. adjective
1.
Synonyms: fast 3, breakneck, expeditious, expeditive, fleet, harefooted, hasty, rapid, speedy, swift
Related Word: agile, brisk, nimble; abrupt, impetuous
Idioms: quick on the trigger
Contrasted words: dilatory, laggard, leisurely, slow, unhasty, unhurried; comatose
Antonyms: sluggish
2.
able to respond without delay or hesitation or indicative of such ability
very quick in perception
his quick eye spotted the trouble
Synonyms: apt, prompt, ready; compare instantaneous
Related Word: clever, intelligent, quick-witted, smart; adroit, deft, dexterous; acute, keen, sharp; able, capable, competent, effective, effectual
Contrasted words: comatose, lethargic, logy, poky, torpid; crass, dense, dull, dumb, stupid
Antonyms: slow; sluggish
3.
Synonyms: wise 4, canny, hep, knowing, nimble-witted, quick-witted, sharp, sharp-witted, slick, smart
II. adverb
Synonyms: fast 2, apace, expeditiously, flat-out, hastily, lickety-split, posthaste, rapidly, speedily, swiftly
III. noun
Synonyms: center 3, core, heart, pith, root