When a male incorrectly assumes that he knows more about a topic that the other person in a conversation, usually a younger woman. Then, proceeds to explain the topic in a condescending tone, as if the other person has no knowledge on the topic and is generally ill-informed.

1) When a man who has no expertise in something tells a female, who is an expert how something works, is, or came to be. 2) When a man repeats what has just been said by a woman and presents it as his own idea 3) when men can't stand anything that questions their egos and thus change the meaning of terms so they don't look like idiots.

When a man attempts to explain to a woman her own job/ idea back at her then gets offended because they don't understand how smart they are. Often used as a term by women to try to explain to men how offensive and derogatory this behaviour is, but taken personally by insecure men who are afraid of treating women equally with respect. These men typically try to use Feminism - the belief that women should be treated with equality - as a bad word. The fact that being sexist is just as bad as being racist is not likely to occur to mansplaining men.

When a male tries to explain something to a woman, and thinks he as to dumb down the explanation, especially when she is at the same level of knowledge, or has more, than her male counterpart.

When a man tries to explain something to a woman in a way that belittles them solely for their gender, assuming all women are incompetent. Author and activist Rebecca Solnit is credited with creation of the term.

When a know-it-all man (read: most) explains something to a woman in the most dickish, condescending, patronizing way possible, never realizing she already knows what he's talking about (read: she has a PhD in the topic), often leading to the woman nodding in vague, wide-eyed agreement that says, "I hope no one EVER fucks this guy, ever."

Men who open there legs to see there little friend.