A very sneaky foreplay moved performed by short Jewish guys from Long Island. Not realizing that the girl is not into him while sitting on her couch, the dude places his hand in between the girl's thighs and flaps it back and forth in the same motion as a fish out of water. The flounder is normally followed by dog-like leg humping.
If performed properly, the flounder-leg hump trick is good way to ensure the "No Pants in the Bedroom" rule is followed. If awkward while doing this move, the dude is usually sent on his way hoping to catch the end of Rosh Hashanah dinner.
"When Yaacov tried the flounder, the date was over."

"I wasn't into Isaac at first, but, after he floundered me, I got to see that my pants really did match the rug...and he found out the color of the carpet"
by Irish-Italian Manwhore September 25, 2006
The true definition of a flounder is a shapeless woman who has neither breasts nor an ass. She is thinly shaped up and down much like the fish.
The flounder originally thought she was cute until she discovered that she lacked any sexual organ that would catch the eye of the opposite sex.
by Lord Price XI April 5, 2009
Tits like 2 flounder fish. The type that need a belt rather than a bra
She hid her flounders with a nice belt
by Montiero is the worst Chris November 17, 2020
A flounder is the act of pushing one's buttocks together while standing and defecating, resulting in two brown smears forming on each of the buttocks. These smears each are flat, brown, and circular, much like the shape of the flounder fish. Floundering is preferably done in the shower, so that one can simply rinse the flounders off when done, and no one has to know about it.
Matt told me about how he gave himself a flounder last night, and went into way too much detail. Gross!
by ehuzzah August 14, 2020
noun - a lazy, goodfornothing person who doesn't excel or accomplish anything in life
Craig is such a flounder! All he does every day at work is sit in his office with his feet propped up on the desk reading the Wall Street Journal.
by Bubbe September 1, 2005