Justin Timberlake found himself in hot water after calling Madonna his "mother chucking ninja" on Twitter in honor of her 56th birthday Credit: Mike Marsland/WireImage.com; Kevin Mazur/WireImage.com

Justin Timberlake found himself the target of widespread Twitter outrage this weekend when he allegedly sent Madonna a birthday tweet calling her his "mother chucking ninja." Followers quickly pounced on him for his use of the phrase, which is sometimes understood as an alternate way of saying "mother f---ing n---a."

The tweet, which has since been deleted, reportedly read: "A happiest of Bdays to my mother chucking ninja, @Madonna!! Hope you have a great one, M!"

Users took him to task immediately after it was posted, responding with tweets like, "I just ended my relationship w/Justin," and "Get Justin Timberlake the f--k out of here." 

As Grantland pointed out in 2012, "ninja" has been used in the past by other stars, too. Katy Perry, for example, substituted it when she covered Kanye West's "N----s in Paris" during a Radio 1 performance that year.

No doubt because of the outrage, Timberlake deleted his birthday message to his "4 Minutes" duet partner Madonna, who turned 56 on Saturday, Aug. 16. One day later, he retweeted a message from Matt Morris about the events in Ferguson: "The world is watching #Ferguson. [And we pray.]"