Tumbletard
One who says things that are retarded on Tumblr. Usually in reference to the LGBTQ community. They are known for calling people misogynistic, racist, sexist, and other such discriminatory adjectives.
I went on Tumblr and said I'm new here. I said I'm a white Christian straight male, and i received hundreds of hate comments calling me a rapist, sexist, racist, misogynistic bigot. The commenters were all tumbletards.
Tumbletard
A douschebag.
That kid Grant is a tumbletard.