cut to the quick

Synonyms:
1. fleet, expeditious. Quick, fast, swift, rapid describe speedy tempo. Quick applies particularly to something practically instantaneous, an action or reaction, perhaps, of very brief duration: to give a quick look around; to take a quick walk. Fast and swift refer to actions, movements, etc., that continue for a time, and usually to those that are uninterrupted; when used of communication, transportation, and the like, they suggest a definite goal and a continuous trip. Swift, the more formal word, suggests the greater speed: a fast train; a swift message. Rapid, less speedy than the others, applies to a rate of movement or action, and usually to a series of actions or movements, related or unrelated: rapid calculation; a rapid walker. 5. abrupt, curt, short, precipitate. 7. nimble, agile, brisk. 10. See sharp.

Antonyms:
1, 10. slow.

Usage note:
The difference between the adverbial forms quick and quickly is frequently stylistic. Quick is more often used in short spoken sentences, especially imperative ones: Come quick! The chimney is on fire. Quickly is the usual form in writing, both in the preverb position (We quickly realized that attempts to negotiate would be futile) and following verbs other than imperatives (She turned quickly and left). See also slow, sure.