fall out
phrasal verb with fall verb uk/fɔːl/ us/fɑːl/ fell | fallen
(TOOTH/HAIR)
（牙齿或头发）脱落，掉落
If a tooth or your hair falls out, it becomes loose and separates from your mouth or head.
Her baby teeth are starting to fall out. 她婴孩的乳牙开始掉落了。
A side effect of the treatment is that your hair starts to fall out. 这种治疗的一个副作用是头发开始脱落。
(ARGUE)
B2 informal吵架;失和
to argue with someone and stop being friendly with them
He left home after falling out with his parents. 和父母吵了一架后，他离开了家。
She'd fallen out with her boyfriend over his ex-girlfriend. 她为了男友前女友的事和男友闹翻了。
(SOLDIERS)
原地解散;离开队列
If soldiers fall out, they move out of a line.
"Fall out, men!" shouted the sergeant-major. “原地解散！”军士长喊道。
Compare: fall in (SOLDIERS)