frottage
Frottage (or "dry humping") is a sex act without penetration that can include any form of sexual rubbing, whether naked or clothed, for arousal or orgasm.
For tagging purposes, use this tag when one person's crotch is rubbing against another person's body, except for genital-on-genital contact (use grinding, buttjob, tribadism, bulges touching, or penises touching for this).
Use dry humping when genital-on-genital contact is stopped by clothing.
Use crotch rub for rubbing against inanimate objects.