A French acronym.
"Toi Même Tu Sais" (a sort of "You Know What I Mean")
Generally use by wesh girls in a private joke with friends.
Trop bien ces délires avec toi emilie, tmtc!!!
Too many to count, mostly used in industry where counting things comes up but it could also be used in every day language, as in:
Q: damn looket all dem foos! how many u think there are?
the number of bacterial colonies on my peetre dish was over 200 therefour it was TMTC.
pennies in the jar are TMTC