Gensplaining is when someone of a very different generation from you thinks they know more than you about something you are an expert in, mainly due to the era you were born / grew up in, and condescendingly takes the time to 'explain' to you how it works (similar to mansplaining).
A 25 year old kid in a shop tried to gensplain to me all about vinyl records and how they related to the length of radio singles 'back in the 70s' the other day; she must have missed the fact I'm over 50 and actually lived through it, or else thought I was senile.
by Golden years June 21, 2017