1.Fig. to marry a mate. We tied the knot in a little chapel on the Arkansas border. They finally tied the knot.
2.Fig. [for a cleric or other authorized person] to unite a couple in marriage. It was hard to find somebody to tie the knot at that hour. It only took a few minutes for the ship's captain to tie the knot.
Get married; also, perform a marriage ceremony. For example, So when are you two going to tie the knot? or They asked their friend, who is a judge, to tie the knot. [Early 1700s]