The term "douchebag" generally refers to a male with a certain combination of obnoxious characteristics related to attitude, social ineptitude, public behavior, or outward presentation.
Though the common douchebag thinks he is accepted by the people around him, most of his peers dislike him. He has an inflated sense of self-worth, compounded by a lack of social grace and self-awareness. He behaves inappropriately in public, yet is completely ignorant to how pathetic he appears to others.
He often talks about how cool, successful, and popular he is, yet never catches on to the fact that he comes across as a total loser. Nevertheless, he firmly believes that he is the smartest, most desirable, and most charming person in the room... and will try to bad-rep anyone who would threaten to expose this facade.
He fancies himself a ladies’ man, yet tends to be a joke to all but the most naive of women. He tries to portray himself as part of the in-crowd (a fashionista, an upwardly mobile professional, the life of the party, etc.) but only succeeds in his own mind.
To everyone else, he is an annoying and arrogant phony who comes across as a wannabe overcompensating for his insecurities. He tries to appear like the center of whatever group will tolerate him, but in reality, he is just a tag-along who mooches drinks, women, contacts, social standing, and other benefits from the group... while contributing nothing.