When your shorts, boxers, or briefs are just loose enough for your man-junk to fall out.
Oh man, I sat across from grandma at the barbecue and had a flopsy. She TOTALLY saw the frank and beans.
di j-to-the-r 25 aprile 2009
When a man and a women are about to have sex, but the man loses his erection when his penis contacts her vagina
"Man I was about to get some last night but I went flopsy."
di Mcdrizzle 13 febbraio 2010
When a person (typically a girl) sticks her thumb up man's butthole and flips around his balls between her fingers.
"Ryan just told me that Sarah's flopsy giving abilities are unmatched!
di IMW 05 aprile 2008