I assume it's some slang that comes from ゴリラ perhaps. I found many examples of it being used in completely different situations and now I'm very confused... Apparently there is even a small book about its meaning, haha.
It seems that the author of ゴリってる会話集 doesn't know the meaning of ゴリる. He just used it as a meaningless word which just sounds odd.
So this book only proves that ゴリる is not an established word :-)
That said, ゴリる is a possible word made up from ゴリラ using this rule. It would mean "be like a gorilla", "do something like a gorilla", etc. You may find ゴリる in rhythm game contexts because ゴリラ is slang for an incredibly skillful player.
1So ゴリってる = gorilling? :) "It's a gorilling story!" That kinda works, since it almost sounds like thrilling -- and it's also nonsense in English, much like that author's use of ゴリる. Apr 8, 2016 at 21:18
Exactly, it's gorilling!– narutoApr 9, 2016 at 2:40