R&R can mean:

• Remove and refit; to remove a component from a vehicle to repair it or to gain access to other components, and then re-install it.
• Rest and Recuperation, or Rest and Recreation, terms used by the U.S. military for short vacations given to soldiers in wartime. Also said Rest and Relaxation.
• Repeatability and reproducibility — see accuracy and precision
• Rescue and resuscitation — see surf lifesaving
• Read and review — a term used in fanfiction by authors looking for feedback