A fork of Rural Dictionary
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