act out of character

Translations
вести себя нехарактерно
She acted out of character when she yelled at her friend.
Она вела себя нехарактерно, когда накричала на свою подругу.
Definitions
To behave in a way that is unusual or not typical for a person, differing from their normal habits, personality, or expected behavior.
Words
character

noun
персонаж
act

verb
действовать
act out

verb
разыгрывать