Definitions of crack:

• noun:   a usually brief attempt

  Example: "He took a crack at it"

• noun:   a purified and potent form of cocaine that is smoked rather than snorted
• noun:   a blemish resulting from a break without complete separation of the parts

  Example: "There was a crack in the mirror"

• noun:   a sudden sharp noise

  Example: "The crack of a whip"

• noun:   a long narrow opening
• noun:   the act of cracking something
• noun:   a narrow opening

  Example: "He opened the window a crack"

• noun:   witty remark
• noun:   a chance to do something
• noun:   a long narrow depression in a surface
• verb:   make a very sharp explosive sound

  Example: "His gun cracked"

• verb:   break into simpler molecules by means of heat

  Example: "The petroleum cracked"

• verb:   reduce (petroleum) to a simpler compound by cracking
• verb:   become fractured; break or crack on the surface only

  Example: "The glass cracked when it was heated"

• verb:   cause to become cracked

  Example: "Heat and light cracked the back of the leather chair"

• verb:   break partially but keep its integrity

  Example: "The glass cracked"

• verb:   tell spontaneously

  Example: "Crack a joke"

• verb:   hit forcefully; deal a hard blow, making a cracking noise

  Example: "The teacher cracked him across the face with a ruler"

• verb:   make a sharp sound
• verb:   break suddenly and abruptly, as under tension
• verb:   pass through (a barrier)

  Example: "Registrations cracked through the 30,000 mark in the county"

• verb:   suffer a nervous breakdown
• adjective:   of the highest quality

  Example: "A crack shot"