Verb that happens when someone gives a sip of their beverage (perferabally a canned beverage) and the person who's drinking puts their mouth all over it.
Matt- Hey there Sally, can I have a sip of your new beverage straight out of that can?
Sally- Why yes, you can.
*Matt takes a sip*
Sally- What the hell Matt why would you fish-mouth the drink like that, i don't want it now.
When smoking cannabis and one person throws an entire nug in for a pack. because the nug is still attached to the stem, the stem will stick out the bowl, resembling a mouse tail. To some, it results in a better all around hit or a total and complete waste.
"Yo man is it my turn to pack?"
"Yeah bro, just mouse tail it, throw in the whole nug"