Acronym for Hand Stapled to Forehead. A facetious melodramatic reference, probably originating from the stereotypical silent film heroine, who would roll her eyes and lift the back of her hand to her brow at a dramatic moment (usually prior to swooning). The "stapled" reference generally suggests that the dramatist's hand gets stuck in place, and it can be used as an insult or as an intentionally humorous melodramatic gesture.
fag gamer: Man I've been smoking a pack of camels while playing BF2, and my HSF siezed up from all the ash.
ME: What happened then?
fag gamer: BF2 then crashed and my stats didn't update.
ME: boo fuking who.