Pretty simple. Run rvm implode
.
After that's done, check you .bash_profile (or similar shell startup script) for the line that loads the rvm environment. It looks something like
[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"
Delete that line.
Finally, delete ~/.rvmrc
, if it exists.
Close out all your terminals, and you're now free of rvm.