What is Boy Brief?
today i leaned, “boy brief” is women's panty with manhole.

the interesting thing here is that, we don't have male underwear that's “girl's panties”.
this is because, female decorate their sex garments to attract attention, and attracting attention is importat because flashing pussy is primary way to signal sexual receptance.
male flashing dick does nothing, because it's female's timing has biological significance.