verb

• (intransitive) To form cracks.
  "It's been so dry, the ground is starting to crack."
• (intransitive) To break apart under force, stress, or pressure.
  "When I tried to stand on the chair, it cracked."
• (intransitive) To become debilitated by psychological pressure.
  "Anyone would crack after being hounded like that."
• (intransitive) To break down or yield, especially under interrogation or torture.
  "When we showed him the pictures of the murder scene, he cracked."

noun

• (slang) Crack cocaine, a potent, relatively cheap, addictive variety of cocaine; often a rock, usually smoked through a crack-pipe.
  "crack head"
• (slang) Crack cocaine, a potent, relatively cheap, addictive variety of cocaine; often a rock, usually smoked through a crack-pipe.
  "kitty crack"
• (onomatopoeia) The sharp sound made when solid material breaks.
  "The crack of the falling branch could be heard for miles."
• (onomatopoeia) Any sharp sound.
  "The crack of the bat hitting the ball."

noun

• (obsolete) One who excels; the best, especially a winning racehorse.
  "Stanton had at one time a reputation for inaccessibility, but that has long since become a thing of the past, […] So that the gallops of the cracks' can, in most cases, be regularly watched and their daily doings truthfully chronicled."