Green’s Dictionary of Slang

tighty-whitey n.

1. (US campus, also tightie whities) in pl., men’s briefs.

[US]Indiana Gaz. (PA) 24 Apr. E-6/2: Fruit of the Loom [...] a common shorthand for those old tighty-whities.
[US]Eble Campus Sl. Apr.
Online Sl. Dict. 🌐 tightie whities n 1. men’s briefs. (‘Are you wearing tightie whities?’).
[US]‘Randy Everhard’ Tattoo of a Naked Lady 219: My dick [...] poked its head through the fly in my tightie whities.
[US] 🌐 Hazed Recruit. Bound and gagged but rock hard in his tighty whiteys this twink will do anything to please.
[US]E. Beetner ‘Zed’s Dead, Baby’ in Pulp Ink [ebook] I can only imagine the back already soaked down to his tighty-whiteys.
[US]J. Stahl Happy Mutant Baby Pills 26: Adjusting the lunchmeat in my starchy, state-issue tighty-whiteys [...] I suddenly remembered my grandmother’s hands.
Twitter 13 Jan. 🌐 Trump allegedly chased a porn star around a hotel room ‘in his tighty-whities’.
[US]T. Pluck Boy from County Hell 249: 4-Hondo wore nothing but baggy sweat-stained tighty whities and a pair of size nineteen engineer boots.

2. (US) a tight, white T-shirt; also attrib.

[US]J. Stahl Plainclothes Naked (2002) 112: All three wore tighty-whitey T-shirts to show off their pecs and biceps.