Spontaneous Erection Syndrome: Affecting usually young teenage males 12-15 years old in which they unfold an erection randomly for no apparent reason. Similar to females' "PMSing", this term can refer to the embarrassing occurrence of this event.
Jimmy: "Did you just see Ben get a boner? I think he wants to get it on with Mrs. Patterson!"
Gerald: "Nah bro, he's just SESing."