An abbreviation for the phrase "I'll slap you (u) bitch!"
Commonly used by angry nerds asleep in bed at night talking to their imaginary girlfriends. It can also be used in the pase tense such as "I slapped ur (your) bitch!"
Examples of I.S.U.B.
"ISUB if you don't pull harder!"
"Last night ISUB"
"Last night, I slapped your bitch!"
"I'd slap you bitch!"
"I'll slap you bitch!"
T.Y.D.S.I.M.W.M.H.B.B.I.U.I is from the famous song Washing Machine Heart by Mitski, For example the lyrics “Toss your dirty shoes in my Washing Machine Heart. Baby, Bang it up inside.”