RMD stands for Required Minimum Distribution. It's the minimum amount of money you're required to take out of your retirement plan once you turn 70 1/2.
RMD rules apply to all employer-sponsored retirement plans such as
pensions, profit-sharing, 401(k), 403(b), and 457(b) plans, as well as
Traditional IRAs and IRA-based plans such as SEPs, SARSEPs, and SIMPLE
IRAs. However, RMDs are not required for Roth IRAs while the owner is
still alive.
Your 1099-R issuer is required to follow RMD rules and regulations,
so if you received a distribution and you're at least 70 1/2 years
young, you can be almost certain you received an RMD. Check with your
plan administrator if you're still not sure.