Green’s Dictionary of Slang

stuffer n.4

[they are stuffed full of ego]

(UK juv.) one who is very pleased with themselves.

OnLine Dict. of Playground Sl. [Internet] stuffer n. Used to imply a person who is extremely self satisfied, egotistical, arrogant, pompous, who will certainly boast about their sexual conquests, but most likely would like to partake in a relationship with themselves.