Definition taken from an episode of Scrubs.
Gomer was a character in the "Andy Griffith Show" and "Gomer Pyle, USMC" on televison from 1963-1970.
"She walked in on you and your sister?!"
"YOU KNOW WHAT I MEAN! Effin' Gomer."
acting stupid, making an ass out of him/her self, being in a blonde moment, ignorant, neive, an idiot, someone who is clumsy.
Literally: Get Outta My E. R.