v.1. To allow something or someone to go or get up: Stop wrestling me and let me up!
2. let up on To release or diminish the pressure on someone or something; ease up on something: Let up on the clutch slowly or you'll stall out the engine. Let up on the new workers; they're doing the best they can.
3. To slow down; diminish: The weather got cold, but the protesters didn't let up in their efforts.
4. To come to a stop; cease: The rain let up, so we went outside and played.