Complex sentence: The term first appeared in public debate when a feminist anti-manspreading campaign was started on the social media website Tumblr in 2013; the validity of the term had not been established until the "Oxford English Dictionary" added it as a word in August 2015.
Split into simpler sentences: The term first appeared in public debate when a feminist anti-manspreading campaign was started on the social media website Tumblr in 2013. The "Oxford English Dictionary" added it as a word in August 2015.