Shareef O'Neal Shows Off Gnarly Heart Surgery Scar, '#Zipperboy'

Shareef O'Neal just revealed his heart surgery scar for the first time Wednesday ... and he's already given himself a new nickname, "Zipperboy."

TMZ Sports broke the story ... Shareef needed a heart procedure done after UCLA doctors detected an abnormality during a routine check-up.

O'Neal went under the knife on Dec. 13 ... but came out of it just fine -- and when he finally got a look at the scar this week, he was able to joke about it.

"My first time seeing my scar ..... #zipperboy."

The operation doesn't seem like it was a laughing matter though ... the scar runs from the top of his chest to halfway down to his belly button!!!

The good news ... Shaq told us just several days ago his son's doing okay -- and could be back on the basketball court in just a few months.