Amanda Bynes' favorite word on Twitter seems to be "ugly" -- and now, she's branding another former child star with her trademark insult.

"Ur ugly," she tweeted late last night. Her target: Miley Cyrus.

The photo she shared along with the message was one of the singer from the Billboard Music Awards.

Miley spoke out about Amanda's tweets this morning on Hot 99.5, calling it "sad" and "hilarious" -- listen below:

Bynes also defended herself for her many online rants -- tweeting "This is my twitter. I say whatever I want. Thanks!"

The attack comes days after Bynes made a Twitter move on Miley's (maybe) man, Liam Hemsworth.

"Liam Helmsworth is the most gorgeous man on the face of the earth other than Tanz Watson. FYi!," she tweeted last week.

No word on what prompted Amanda's attack ... but, is it just us, or don't the two kinda look alike, especially in Bynes' latest mug shot?

See more former good girls gone bad in the gallery above.

Hot Videos