brass ones

Brass balls, one would assume.

Eidolon's Nepenthe: Brass ones!

by Kung-Fu Jesus June 11, 2006

big brass ones

Large set of testicles; used to describe the perceived guiding force behind a particularly courageous or audacious action undertaken, usually, by a man.

"Standing up to that mugger by himself revealed John had a set of big brass ones."

by JKB - Charleston, SC June 15, 2014