1.
If someone in authority lets you off a task or duty, they give you permission not to do it. (mainly BRIT)
In those days they didn’t let you off work to go home very often.
PHRASAL VERB: V n P n/-ing
2.
If you let someone off, you give them a lighter punishment than they expect or no punishment at all.
Because he was a Christian, the judge let him off...
When police realised who he was, they asked for an autograph and let him off with a warning.
PHRASAL VERB: V n P, V n P prep/adv
3.
If you ~ an explosive or a gun, you explode or fire it.
A resident of his neighbourhood had ~ fireworks to celebrate the Revolution.
PHRASAL VERB: V P n (not pron), also V n P