Usher blasted his ex-wife in court today -- testifying that Tameka Foster flew into a jealous rage, hitting him, throwing food, and worst of all ... spitting on his girlfriend.
Usher took the stand in his ongoing child custody trial with his ex, and under questioning by his attorney, revealed how Tameka once went ballistic and "wanted to fight" ... when he showed up at her house with his new sidepiece.
Ush testified Tameka walked to his car and said, "I'm gonna kick your ass. Bitch get out of the car. How dare you bring this woman into my subdivision in my house?"
He added, "She continued to spit. At this point she pulled the door open, tried to swing at her."
Usher claims he had to get out of the car and block Tameka ... who then hit him. Usher said he pleaded with Tameka to calm down, but claims "she threw a plate of food at the car" ... as he fled the situation.
You gotta hear Usher describe the intense showdown -- and remember, Tameka previously testified she once told the gf, "I will f**k you up."