A person from another planet, usually Mars, A.K.A a martian. The word stems from Costhanino, the word for pig head in the language of the lost Hawaiian civilization. Thanin can also refer to someone who suffers from intense annoying syndrome, someone who constantly pokes people, or in some cases, someone who suffers from hereditary retardation.
Oh My Gandhi! That idiot is such a Thanin.
That Thanin is so weird, I bet he's a martian!