Green’s Dictionary of Slang

retard n.

also retardo

(orig. US) derog. ref. to a mentally retarded person, whether actually or fig; also as adj.

[US]Baker et al. CUSS 184: Retard – A person who always does the wrong thing. A person without much social or academic ability.
[US]T.C. Bambara ‘The Lesson’ in Gorilla, My Love (1972) 88: Miss Moore asking us do we know what money is, like we a bunch of retards.
[UK]D. Gram Foxes (1980) 17: We’re going to school, retardo.
[US]J. Ellroy Brown’s Requiem 190: For treating me like a slave! Like a retardo!
[US]S. King Christine 247: You can laugh, you retard.
[US]R. Campbell Sweet La-La Land (1999) 218: He’s this retard used to hang around Bitsy.
[US]J. Stahl Plainclothes Naked (2002) 207: You think ’cause I’m part Rican, I’m some retardo punk?
[UK]G. Iles Turning Angel 162: I’m not sure why I tried out except that it’s what you’re supposed to do. I’m such a retard.
[UK]S. Kelman Pigeon English 60: Don’t be a retard, you can’t just ask for it straight out.
Dly Pennsylvanian 23 Mar. 🌐 Other words like ‘retard’ fall under the same category of words with troubling connotations that we casually use.
[Scot]A. Parks May God Forgive 349: ‘People laughing in the street. Dessie Caine fucked a retard and look what he got’.