rock1
  
  n.
      - the hard mineral material of the earth's crust, exposed on the surface or underlying the soil. 
▸a mass of this projecting out of the ground or water.
 ▸
(the Rock)
 Gibraltar.
 ▸a boulder.
 ▸N. Amer. a stone of any size.
 - Geology  any natural material with a distinctive mineral composition.
 - Brit. a kind of hard confectionery in the form of cylindrical peppermint-flavoured sticks.
 - informal a diamond or other precious stone.
 - informal a small piece of crack cocaine.
 - 
(rocks)
 vulgar slang a man's testicles.
 
 
  Phrase
  
    - between a rock and a hard place
 informal faced with two equally difficult alternatives.  - get one's rocks off
 vulgar slang have an orgasm.  - on the rocks
 informal  - experiencing difficulties and likely to fail.
 - (of a drink) served undiluted and with ice cubes.
 
 
   
  Derivative
  
    - rockless adj.
  - rock-like adj.
 
   
  Etymology
  ME: from OFr. rocque, from med. L. rocca.
 
  
    
rock2
  
  v.
      - move gently to and fro or from side to side. 
▸shake, especially because of an earthquake or explosion.
 - cause great shock or distress to.
 - informal dance to or play rock music.
 - informal (of a place) be exciting or full of social activity.
 - 
(rock up)
 arrive; turn up.
 - informal wear (a garment) or affect (an attitude or style), especially in a confident or flamboyant way:
 Iverson was rocking a stars and stripes skullcap.
 
n.
  - 
(also rock music)
 a form of popular music derived from rock and roll and pop music but characterized by a more serious approach. 
▸rock and roll.
 - a rocking movement.
 
 
  Etymology
  OE roccian, prob. from a Gmc base meaning ‘remove, move’.