【敬】对中、老年男性的称呼（一般是对不相识者）。唔该叔记，南华新街点行啊？（请问大叔，南华新街怎么走？）

an appellation used to address a middle age or elderly man whose one doesn't know the name of, used in situation such as when talking to a random middle age / elderly man on the street