1 n. small penis, refers to the tendency of small penises to bounce around easily even when erect. Possible derivative of "dinky", or referring to the "dinger" of a bell, which swings back and forth, causing the bell to ring. Generally a derogatory comment.
2. adj. Used to describe someone who is insane or "not quite all there" mentally.
1. When Jane saw Peter's ding-ding of a cock, she about fell out!
The phrase "It's a ding ding" is used when experiencing a big win in Casino games, a win 100x or more is normally required for it to be a Ding Ding. Higher wins 300x or more are often referred to as a SUPER MEGA DING DING.
The phrase is said whilst holding one foot with both hands, then raising it in the air as you say "ding ding"
Legend has it that a Swedish man called Sir Kim from Halmstad created the phrase when getting over 100x on Starburst!