i'm staying in tonight and there's no chance of getting laid, so i'll just grab a pair of b-string underwear
items in your underwear collection that are not suitable for special occasions, and are otherwise ratty underwear that you wouldn't want anyone else catching sight of
"i'm staying in tonight and there's no chance of getting laid, so i'll just grab a pair of b-string underwear" What is the definition of "b-string underwear"?