Uncle/ˈʌŋkl/ Definition 1 of 5Pro Tip 1/2Family Relations Use 'uncle' to refer to a close family relation, specifically your parent's brother or aunt's husband. I spent the weekend with my uncle and cousins. Pro Tip 2/2Extended Family 'Great uncle' refers to your grandparents' brothers; they're part of your extended family. My great uncle used to be a sailor.