In American English slang, a “Douche” is a person that is an idiot, stupid, unpleasant, rude, annoying, etc. There is no one specific meaning of this word. But in colloquial American English, “Douche” is used to describe someone in a negative way.
Literally, a douche is something that is used to clean the vagina.
Example: “Don’t invite Marcus, he is such a douche.”
Example: “I feel like a total douche right now.”