The act of a guy and a girl going into a closet at their friend's house, in order to get away from the sounds of their other friends getting busy on the futon in the living room. The guy and the girl in the closet then get busy themselves.
Closeline laughing occurs when you start laughing hysterically in a high pitched tone and then randomly dropping a couple octaves (think squirrel laugh to lumberjack laugh in a matter of seconds!). The promiscuous lady, from The Notebook, does this after watching street lights change, like the adventurous southern girl she is.
Jane ran merrily along giggling, until she ran into a low tree branch, causing her to closeline laugh and lose all her friends for sounding like a dike.