thumb me dumbly

Thumb me dumbly is the acting of taking the nearest mentally challenged person (or group of persons depending on how fucked up you are) and having he/she/them insert their thumbs into your anal cavity

Guy 1: so what did you get up to last weekend bro?
Guy 2: I went to the loony bin and got a few retards to thumb me dumbly
Guy 1: you’re a sick little cunt you are