IPA: /ˈɡruːmz.mən/
KK: /ˈɡrumzˌmæn/
A man who helps and supports the groom during a wedding ceremony.
John was honored to be chosen as the groomsman for his best friend's wedding.
Groomsman → The word is formed from "groom" (from Old English *guma*, meaning man or male) and "-sman" (a suffix denoting a person associated with a particular role). A groomsman is thus a man associated with the groom, typically serving as a supporter or attendant during a wedding.
Think of a 'groom' as a man getting married, and the '-sman' means a person associated with him. This helps you remember that a groomsman is a man who supports the groom.