I hadn't heard the term "mansplaining" before but I ran into it today. It's when a man, assuming he knows more than a woman without asking, explains something to a woman that the woman already knows. Best done with a dollop of condescension and paternalism.
My father used to do this all the time to my mother. He took a six-week emergency medical course in the sixties as training to be a medic in the National Guard. He never actually used any of that training. My mother, on the other hand, got her bachelor's in Nursing, was a certified Critical Care Registered Nurse, and worked in a hospital for over a decade. But my father would still explain medical things to my mother, since his six weeks of training made him an expert. Or something.
I'm pretty sure that if I were a woman and this happened to me a lot, it would drive me nuts. Since it drives me nuts now when people explain stuff I already know to me, and that's without the extra condescension and paternalism involved in mansplaining.
The reverse of this happens to me a lot at fabric stores. Women who work at fabric stores (or yarn stores) seem to assume any guy who wanders in is lost, looking for his girlfriend/wife, or completely confused and overwhelmed in his ignorance. One time, I was replicating a costume from a film that was made of linen. I got some linen that matched pretty well and took it to the cutting counter. And got a five minute lecture from the woman about the properties and appropriate uses of linen before she would cut the fabric for me.
I couldn't get a word in. She finally wound down by noting that linen wrinkles easily (a fact I was quite aware of already), and said, "Now that you know all that, is this what you want?"
I said, "Well, since the costume I'm replicating was made of linen, and I'm making a screen-accurate reproduction, I don't think it would make sense to randomly pick some other fabric, would it?"
I actually know so much about fabrics that I have ended up helping other customers pick out what fabrics they should use. But still the women at the fabric store assume I am some poor befuddled idiot man-child like the they see on TV sitcoms and take it upon themselves to enlighten me about fabric because I couldn't possibly know what I'm doing.
It gets to be annoying after a while. If what happens to me sometimes at fabric stores happened to me a lot more generally, in the world at large, I think I would probably become very irate.
Another quick example: Just last summer, after ten years or so of sewing, I went into a fabric store in Ohio and the women saw fit to test me when I claimed I knew what I was doing! One said, "Okay, when you are ordering fabric, what measurement do you use?"
For a second I was confused because it was such an easy question that I thought it was a trick or something. So then I said, "Yards." Only then did they accept that I knew what I was talking about.
So, I can only imagine how much it would piss me off if this happened to me all the time. I'd probably be tempted to coin a term for it too.
I wonder if I've been guilty of it myself, but I think technically I probably haven't. That is to say, I have most certainly (on any number of occasions) explained something to someone that it turns out they already knew, not bothering find out if they knew it first. Some of those people, certainly, have been women. But I didn't do it because I thought that I, as a man, knew more than her, as a woman. It's because I generally think (sometimes incorrectly, I admit) that I, as me, know more than anyone else -- man or woman -- as not me. I have the more general failing of thinking I know more than everyone else instead of the more limited failing of thinking I know more than women. So, technically, I don't think I'm guilty of mansplaining, though I suppose the difference is pretty academic.
One other funny example of reverse mansplaining I have experienced: A few years ago I moved to a new state to join my girlfriend. We were driving to the bookstore or something and drove by the local mall. She says to me, "Here's the mall. You should avoid this area around Christmas. It gets really busy here around that time."
I replied, "It gets busy at the mall at Christmas time? Really? I'm shocked. Oh, no, wait, I'm not, because I've actually lived in America before."
Who doesn't know it gets busy at the mall at Christmas? Jeez.