This is the day when you get to playfully slap the ass of your bestfriend of the opposite gender. That's where the his/her part comes from
Yo did you know tomorrow is national slap "his/her" ass day
by Jake Wall April 11, 2017
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Slap her ass

When you slap her ass. duh
when u really wanna slap her booty
Hey check out her gyatts!
John: Slap her ass, dude
by boxybooawesomeTENNIS November 15, 2023
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