Usher Accused of Cheating With Bridesmaid

Usher was being cross-examined by Foster's lawyer this week in Fulton County court ... about his claim that Tameka brings nannies in and out of their children's lives.

Tameka's lawyer asked Usher if one of the nannies in question had "left Miami because you were discovered in bed with Maya Fox Davis?" Sources close to the couple tell TMZ Davis was a bridesmaid for Tameka ... and the alleged incident happened during their marriage.

Usher's attorney quickly objected, but you gotta watch the clip to see how it played out in court. There's also a contentious exchange between Usher and Tameka's lawyer regarding that whole spitting incident.