A combination of New York Knicks point guard Jeremy Lin's last name and the word insanity. It has been used by NBA stars, sports pundits, celebrities and fans alike to describe the phenomenon surrounding the player who went from being overlooked by multiple teams to breaking records in one week. The unlikelihood of this occurrence is what makes it so contagious.
Guy 1: Did you see Jeremy Lin's game winning 3 last night?
Guy 2: Yea man, he's amazing. Linsanity is spreading really quick.