Rock

Rock has several meanings:

• rock (geology), a hard substance made of minerals, often found in or on the ground
  • A metaphor derived from the above meaning: someone you trust and depend on. A person might call a trustworthy and reliable friend "a rock".
• a verb, to rock, meaning to move to and fro:

1. The mother rocked her baby.
2. The boat rocked in the wind.

• Rock and roll music, a form of popular music from the 20th century. *The word "rock" is short for "rock 'n roll". Sometimes it refers to music with a "harder" sound than the original 1950s "rock 'n roll" sound.