When someone is in front of you and without warning you get your hand between there thighs and slap there thighs back and forth saying "SlappySalmon"
I was behind my friend walking up a flight of stairs and it was a perfect opportunity to give him a slappy salmon. I gave him a slappy salmon and he turned around and yelled "knock it off" he was pissed.
Standing in front of your significant other, or someone else, with a bigsmile, swinging your junk back and forth so it slaps against your legs. Works best right after you get out of the shower.
When Brandon got out of the shower he showed Cassieslappyslappy so she would wake up.