A man who attends the bridegroom at a wedding.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "groomsman" in a sentence
"You must know that we Venetians have a saying that the groomsman is the godfather of the first child."
"His groomsman was a first cousin of Lucinda's, and no one else was in the room but the servants of the house."
"DEAR ED: You can decline by saying, "Cousin -- you're so nice to ask me, but being a groomsman is a young man's game."