Manspreading is defined by the Oxford Dictionary as:
The practice whereby a woman, especially one travelling on public transport, adopts a sitting position with her legs wide apart, in such a way as to encroach on an adjacent seat or seats.
The earliest known reference to the term is apparently from an October 2014 article in AM New York which referred to woman spread. The term would later be popularised as woman spreading. Prior to the development of the term significant discussion occurred online following the launch of the Tumbler blogs Women Taking Up Too Much Space, One Sis Two Seats and Saving Room For Cats.
Mainstream news sites such as New York Magazine have described manspreading as a microagression. The Telegraph, the Globe and Mail and many other sources suggest this is a mainstream idea within masculism.
As Breitbart indicates women have been arrested for manspreading in the last couple of years.