To use both hands to smack one's scrotum and balls back and forth repeatedly until the sack is deeply reddened and sore to the touch. Performed for sexual pleasure and by those into rough genital play. May be self-performed or performed by a mate.

Male masturbation. Typically, the more vigorous and rough variety. Not just a causal wank.

Throwing up, vomit

"lez beet it" is common use by american rappers as it refers to doing it in a sexual or violent way.

When something is just so embarrassing, your face turns beet red.

When a man hits a woman's breasts so hard that they become red, and then places his penis between the breasts and tit-fucks her.

The testicles. The balls. The gonads.