let off

Short definition from Wiktionary

Verb

1. 1
   To cause to explode or come out; to release.
2. 2
   To forgive and not punish.
3. 3
   Synonym of leave off.

Noun

1. 1
   An escape from punishment.
2. 2
   A device for letting off, releasing, or giving forth, as the warp from the cylinder of a loom.