Used other than figuratively or idiomatically: see low-background, steel. / Steel with low inherent radiation levels, suitable for instruments and experiments highly sensitive to radiation.

Used other than figuratively or idiomatically: see low-background, lead. / Lead with low inherent radiation levels, suitable for instruments and experiments highly sensitive to radiation.

Pertaining to having a significantly lower level of inherent, background radiation than usual.

(music, slang) Underground or alternative rap music.

plural of backpack rapper

(music, slang) A performer of backpack rap music.

(euphemistic) Synonym of pain in the ass.