This is the 4687th most frequent Russian word.
дурака
"Дурака" means "fool" or "idiot" in English.
The word 'дурака' is used in the phrase 'валять дурака,' which means 'to fool around' or 'to act silly.'
Он валяет дурака.
He's fooling around.
The word 'дурака' is used to mean 'a fool,' and the phrase implies not to treat the speaker as being naive or easily deceived.
Не играй меня за дурака.
Don't take me for a fool.
The word 'дурака' is used in the phrase 'строить из себя дурака,' which implies feigning foolishness for some purpose, perhaps to entertain or to avoid responsibilities.