Green’s Dictionary of Slang

zit n.2

[ety. unknown]

1. [1950s+] (orig. US teen, also zat, zitz, zort) a spot, pimple or blackhead; also attrib.

2. [1960s] (US campus) any form of mark.

3. [1960s] (US campus) a general insult.

4. [1960s] (US gay) an underage boy.

5. [1970s+] a skin blemish left by a lovebite.

In derivatives

zit-faced (adj.)

acned, spotty.

zitty (adj.)

acned, spotty.

In compounds

zit doctor (n.)

[1980s] (US teen) a dermatologist.

zit features (n.) (also zitface)

[1990s+] a general term of abuse, delivered to one who has acne.

zithead (n.) [-head sfx (1)]

[1990s+] (US) a teenager, the image is of acned mediocrity.