A schmassive is a penis of such substantial size it can often be compared with objects such as an Inter Continental Balistic Missile, a zeppelin, a submarine up to such a scale its testicles could be the size of the moon. Following the trend of schlort, schledium and schlong, the schmassive is of such epic proportion to the schlong it is almost separate from the franchise.
Person A: Hey man is my wang a schlort, schledium or schlong dya reckon?
Person B: Ok....Whoa! OMFG that's a fucking schmassive!