1. A mythical creature described as half ant, half lion, with reversed genitalia.
2. Similar to a distress call. If separated from your friends one night when out wreaking havoc, yell Mermacolion. Your lost comrades should respond with the same thus enabling you to find your way back, Marco Polo style. It is not unusual to draw out the ending of the word either.
"Guys, I gotta go take a leak"
ten mins later...
"Uh, guys? Crap. MERMACOLION!!"