An acronym meaning, "Geek In Name Only." It is a corruption of the term "RINO," a political term popular in the early 21st century.
It is used to describe someone who emulate the attitudes, activities, and appearance of dedicated fans; but have no true emotional attachment to it. For them, it is simply a fad they're following rather than true love of a genre.
As a fannish invention, it has no direct analog in American English.