Jewnicorn

Simply put, a Jew with a foreskin.

A "bris"-- the Jewish ceremony for circumcision-- is typically performed during infancy and is widely practiced in the Jewish culture, making it uncommon or rare for penis-bearing Jews to be uncircumcised.

The term "Jewnicorn" is a portmanteau of the words "Jew" and "unicorn" because much like the horny mythical creature, an uncircumcised Jew is a rare sighting.

Person A: "When I hooked up with Rex for the first time I found out he's a total Jewnicorn!"
Person B: "A what??"
Person A: "A Jewnicorn! Anteater! Rumpleforeskin! He's an uncircumcised Jew, a rare, unique, and pleasantly surprising treat!"