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 .