The act of deep mouth and tongue kissing your partner after they have eaten your ass or after you have eaten theirs without any wiping or cleaning of the mouth. Straight from ass to make out.
Rachel was mustard lippin’ me last night. It was tangy.

After my uncle ate my ass, he ended up mustard lippin’ me.

Braaaaahhh your sister tongue punched my fart box last night. It was all good until she started mustard lippin’.
by Eaton Holgoode February 1, 2018
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