anyone or anything small or undersized. can also mean timid weak or being a pussy.
i've caught several fish in this lake but they are all milli-mouths. stop being a fucking milli-mouth and beat that guy's ass!
by tomscrews September 09, 2008
1 more definition
small in stature, timid, scared of confrontation. an all around pussy.
1. I've caught fish in this lake before but they are all milli's or milli-mouths. 2. Don't be such a milli-mouth and whip his ass. 3. That guy is a milli-mouth maggot!
by Thomas Crews August 30, 2008