Definitions by M&F Race

Clacking 

Verb. For one to swing one's scrodum back and forth until a sound is heard. The sound can either be high pitched like a slap, or it can be deep like your ball sack is jelly. While swinging your fellow peers encourage you to trust forward harder, propelling the sack to make an intense clacking noise. The person who makes the louder noise with their ball bag is the champion of NYM&FR.

I thought it could never be done, it was terrible, yesterday I clacked so hard my sac started to bleed profusely. I screamed but luckily my friends were there to massage the pain away.

Clacking by M&F Race May 14, 2005