| Abbreviation | Definition |
|---|---|
| RJ | Random Joust |
| RJA | Redding JuJitsu Academy |
| RJJ | Ranger JuJitsu |
| RK | Rally Killer |
| RK | Red King |
| RK | Roundhouse Kick |
| RKC | Rissington Kart Club |
| RKC | Russian Kettlebell Certification |
| RKD | Right Knuckles Down |
| RKJ | ROTOR KICK, Junior |
| RKO | Randal Keith Orton |
| RKU | Right Knuckles Up |
| RL | Rounds Lost |
| RL | Running Losses |
| RLB | Replacement Level Baseball |
| RLCM | Rugby League Coaching Manual (established 1993) |
| RLFC | Rugby League Football Club |
| RLR | Run, Lynn, Run |
| RM | Repeat Maximum |
| RM | Repetition Maximum |