It means uncle, although in anime character regularly use it in its less formal form where it functions more as "mister" or "sir." It'
s just an informal, but not necessarily rude, way to refer to an older man than yourself that you'
re unfamiliar with.
That's all I wanted to get clear. Most definitions stop at uncle and barely explain the secondary, and probably more common, use for it. "Ojisan"
always means "sir/mister" unless they'
re actually they'
re uncle.