crack down

intransitive verb

1. to make a sudden, sharp noise, as of something breaking
2. to break or split, usually without complete separation of parts
3. 1. to become harsh or rasping, as the voice when hoarse
   2. to change suddenly from one register to another, as the voice of a boy in adolescence
4. Informal to move with speed: now chiefly in phrase , to start moving with dispatch
5. Informal to break down: to crack under a strain

transitive verb

1. to cause to make a sharp, sudden noise
2. to cause to break or split, as by a sharp blow or by heavy pressure, intense heat, etc.
3. to destroy or impair: to crack all opposition
4. to cause (the voice) to crack
5. ☆ to subject (as petroleum) to the process of cracking
6. to hit or strike with a sudden, sharp blow or impact
7. to break through the difficulties of; manage to solve: to crack a secret code
8. Informal to manage to gain entrance or acceptance in
9. Informal
   1. to break open or into; force open: to crack a safe
   2. to open and consume the contents: to crack a bottle
   3. to open and read or study: to crack a book
   4. to open slightly (a door, window, etc.)
10. Slang to make (a joke)

noun

1. a sudden, sharp noise, as of something breaking: the crack of a whip
2. 1. a break, usually without complete separation of parts; fracture
   2. a slight defect; flaw: cracks in his composure
3. ☆ a narrow opening, as between boards; chink; fissure; crevice
4. an abrupt, erratic shift of vocal tone, as from emotion or in adolescence
5. a moment; instant: at the crack of dawn
6. a sudden, sharp blow or impact
7. ☆ Informal an attempt or try: to take a crack at working a puzzle
8. ☆ Slang a joke, gibe, or sharp remark
9. Slang a burglar or burglary

adjective