(v) To completely fail at something.
(n) To be a complete failure.
Origin: From Rooster Teeth's Blaine Gibson, who, while not particularly a failure in his own right, is constantly mocked as one by his co-workers.
Person 1: Did you get a load of Bob trying to do a 360 no-scope and somehow ending up grenading himself?
Person 2: Yeah that was hilarious, he totally blained it!
Person 3: Yeah he's such a blaine.