A familiar, casual term for a middle-aged man or 'uncle' — used colloquially to refer to a middle-aged man, often affectionately or informally.
あそこの店のおっちゃんはいつも元気だ。
The guy who runs that shop is always cheerful.
駅前でおっちゃんが道を教えてくれた。
A middle-aged man near the station showed me the way.
年配の人に対して「おっちゃん」と呼ぶのは礼儀正しくない場合もある。
Calling an older person 'occhan' can sometimes be impolite.