Green’s Dictionary of Slang

1. (Ulster) an unpleasant shock, a major disappointment; thus gunked, disappointed.

1908		L. Doyle Ballygullion 210: I’ll give her a gunk for wanst. [Ibid.] 245: I was a bit gunked at the first to see that thim that didn’t know me was a dale too anxious to find out if the potatoes was good.
1925		L. Doyle Dear Ducks 159: He’ll choke on it, he’ll be that gunked.
1953		L. Doyle Back to Ballygullion 13: You needn’t be looking so gunked.

2. (US) nonsense.

1947		(con. 1944) J.H. Burns Gallery (1948) 318: I’m writing to you because I could always tell you nearly any ole gunk that came into my head.
2000		Guardian G2 23 May 15: The overlay of ‘I’m OK’ gunk [...] reconstructs that reality as something less depressing.

3. (US) a fool, a dullard.

1914		Sun (NY) 10 May 8/2: This is the same gunk who invites the sales manager up to his house to meet his two spot wife and have dinner.
1966–7		in DARE.
2006		Urban Dict. 🌐.

4. (US) anything worthless, unpleasant, undesired.

1931

Hammett Glass Key 511: The nurse came in carrying a large basket of fruit. Isn’t it lovely?’ [...] Frowning at the card, he told the nurse [...] ‘Help yourself to that gunk and take enough of it so it’ll look as if I’d been eating it’.