n.

1. a long narrow opening;
   cleft, crevice, fissure, scissure
2. a narrow opening;
   gap
   
   • he opened the window a crack
3. a long narrow depression in a surface;
   crevice, cranny, fissure, chap
4. a sudden sharp noise;
   cracking, snap
   
   • the crack of a whip
   • he heard the cracking of the ice
   • he can hear the snap of a twig
5. a chance to do something;
   shot
   
   • he wanted a shot at the champion
6. witty remark;
   wisecrack, sally, quip
7. a blemish resulting from a break without complete separation of the parts
   
   • there was a crack in the mirror
8. a purified and potent form of cocaine that is smoked rather than snorted;
   tornado
9. a usually brief attempt;
   fling, go, pass, whirl, offer
   
   • he took a crack at it
   • I gave it a whirl
10. the act of cracking something;
    fracture, cracking

v.

1. become fractured; break or crack on the surface only;
   check, break
   
   • The glass cracked when it was heated
2. make a very sharp explosive sound
   
   • His gun cracked
3. make a sharp sound;
   snap
   
   • his fingers snapped
4. hit forcefully; deal a hard blow, making a cracking noise
   
   • The teacher cracked him across the face with a ruler
5. pass through (a barrier);
   break through
   
   • Registrations cracked through the 30,000 mark in the county
6. break partially but keep its integrity
   
   • The glass cracked
7. break suddenly and abruptly, as under tension;
   snap
   
   • The rope snapped
8. suffer a nervous breakdown;
   crack up, crock up, break up, collapse
9. tell spontaneously
   
   • crack a joke
10. cause to become cracked
    
    • heat and light cracked the back of the leather chair
11. reduce (petroleum) to a simpler compound by cracking
12. break into simpler molecules by means of heat
    
    • The petroleum cracked

adj.

1. of the highest quality;
   ace, A-one, fantastic, first-rate, super, tiptop, topnotch, tops(p)
   
   • an ace reporter
   • a crack shot
   • a first-rate golfer
   • a super party
   • played top-notch tennis
   • an athlete in tiptop condition
   • she is absolutely tops