A sexist term used by misandrist women to disrespect, belittle and devalue the opinion of her male peers in an attempt to make herself appear smarter or better in comparison.
This is common among mixed gender discussions and debates. The term mansplaining is commonly thrown around by those wish to turn the argument into a battle of the sexes or just lack any knowledge or means od adding value to the discussion and wish to devalue the input of other's (in this case males) who are involved in said discussion.
Sue: "I think WWII was hardest on wives back home then the solders."
Bob: "What about the men serving who put their lives at risk during WWII? I think it was harder on them knowing they might die and not see their wife again."
Sue: "Oh there you go again mansplaining!"