伯父
おじ · oji · JLPT N2 · noun
uncle
伯 = eldest/first-born + 父 = father: your father's older brother
伯 marks the eldest sibling, so 伯父 is a father's elder brother. A younger father's brother is 叔父, which is read the same way, oji. Use 伯父 humbly when speaking of your own uncle.