The act of taking ones hand and placing it in someone else underarm and shaking it as if it was a flounder out of water.
I am floundering my friend.
Established Winter of '04. Used to describe the act of flopping around on the sofa all Sunday long. One resembles a Flounder out of water flopping as it gasps for air, in its case, water.
We floundered all day and loved it.