When someone jumps onto someone to injure them (or sometimes killing them)
The person will normally be laden on the victim with there feet, but doesn’t necessarily need to be.
To pronounce, it is simply Mario with ‘ed’ (as in jumped) at the end
As in the computer game on nintendo. The character runs over things. So if you were to jump on/over and run over something, your would be said to be mario'ing the item.