A form of expressing how much you like another person's idea, joke, style, etc by literally lightly touching hands with one another. It is meant to be used in place of giving someone a high five.
"That's so awesome. You're so hardcore. TMH." They lightly touch hands
Debb: I'm goin to TMHS
Tod: Wow. Why don't you just kill yourself now. Really.
"Wow, that guy is TMH."