Misnomer of "Eh Marine".
The act of violently slapping someone across the side of the head, from behind, with enough force to knock them from their seat. Preferably executed whilst the victim is seated in front of a computer. May be accompanied by screaming "EVALINDA!" in a spanish accent (eva-leen-da) just before impact. Should be followed up by a double thumbs-up and a victory dance.
As seen on youtube : /watch?v=mpHLEm9-0bg