A combination of possibly and probably. If possibly gives something a chance from 0% to 50% of happening, and probably gives something a 75% or greater chance of happening, then prossibly is the area between the two, the range of 50% to 75%.
Person 1: Hey, you want to go to the movies on Friday?
Person 2: Prossibly, depends on whether or not my boyfriend has to work.
Person 1: Dag, you can't let him control your life.
Person 2: But he loves me!
Person 1: Lame.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
"Base we've got some square groupers floating outside of Miami harbor."