The squirming and "oh shit/snap/damn/etc" moan from any individual or group, verbally or in thought, when viewing an instance of one's groin area being subjected to physical pain, or hearing of a story describing such an instance.
Usually applies to hearing or viewing stories describing your same gender, but can also be universal.
"Dude, did you hear what happened to James at Bogart's yesterday?"
"Naw, fill us in bro"
"He decided to start crowd surfing, and as he did some asshole punched him in the 'nads"
Everyone: "OH DAAYUUUMMM!"- as they cross their legs, bend over as if to protect their crotch, squint their eyes
"I have nothing but crotch sympathy for James right now..."