A common phenomena that occurs within the groin region of a male's body.
Over 90 percent of incidents are reported by concert-goers, the rest by house party-goers.
It occurs when the bass being played in the surrounding environment turns so loud that is causes a woman's breasts to literally bounce. The male notices the bouncing breasts and continues to stare at them, inducing an erection.
You thought that was a Bass Boner, imagine skrillex.