A man's former boyfriend; an ex-boyfriend (someone you used to date). Common, colloquial term.
私の元彼は去年結婚しました。
My ex-boyfriend got married last year.
駅で元カレに偶然会ってしまって気まずかった。
I ran into my ex at the station by chance and it was awkward.
友達が元彼のことで相談してきた。
A friend came to me for advice about her ex-boyfriend.