Real Time Messaging API in Slack. Don't use for RTM versions of something. For Restricted Transaction Memory, use intel-tsx tag instead.
RTM means Real Time Messaging API in Slack.
It could also mean Release To Manufacturing (or Ready To Market) product state. In this case only appropriate product tag should be used, e.g. just visual-studio, not visual-studio and rtm.
For Restricted Transaction Memory please use intel-tsx, which covers both Hardware Lock Elision and Restricted Transaction Memory.