Collocations for underwear - noun

long
skimpy
thong (esp. AmE)
bikini (AmE)
thermal, warm
cotton, lace, lacy, silk
sexy
ladies', women's
men's
clean, fresh
dirty

change, set
She packed a fresh set of underwear and her toothbrush.

pair (esp. AmE)

in your underwear
I'm getting cold standing around in my underwear.