Secondhand Dong is best described as the awkward moment when one open mouth kisses, tongue kisses, or kisses their significant other/date after receiving a blowjob or receiving information that their significant other/date has given a blowjob.
Bro, it's a bad idea to kiss your girl right now. She just gave you a blowie, and there's no way I'm letting you get Secondhand Dong, dude.
by HexBuster May 25, 2014