A word said aloud when a a person places their arm across the shoulder of the opposite gender, or the same if you are that kind of person. The word must be enunciated and shouted at the top of one's lungs to notify others around you that you have placed your arm across her/his shoulder. The counterpart of this word is "KABOOM" when she/he responds by placing their arms around your abdominal region.
A: "I was at the theater last night and I 'SHABOOMED' my date."
B: "Nice...did she 'KABOOM' you back?
A: "Hells yea, got the whole theater jealous jigger"