When saying "dumbass" is too rude, saying idiot is too serious, and you
feel like they would thumb themselves.
Basically an idiot who fingers himself with his thumb.
Could be a she, but used against is more
powerful but less rude because it sounds silly.
Bob: guys, what the
square root of 2 is 1, right???
Dave: no, thumbass, it's 1.41421356237 simplified heavily.
Bob: it's definitely rational though, right?
Dave: …
Bob: right???????!!!??!?
Dave: this is peak thumbassery...
OR
John: Bob, are you gay? I saw you
eating a burger.
Bob: how are those even related, thumbass? Get your head straight and be straight, it's obvious that you are
extremely gay for Dave.
John: no I'm not... *blushes very annoyingly)
Bob: SHAJOFUGINMOUTH