"Gelivable" means something is cool, or cooperative. And "ungelivable" means just the opposite.
"Gelivable" is a Chinese word in English alphabet, with its original form in pinyin "geili". It used to be a regional dialect meaning something is cool or supportive. "Gei" means "to give" or "to be given." "Li" means "ability" "power" or "force." So together they mean "to give force (to)" "be capable of." For example, when you are downloading at a speed of 1 TB/s, it is very "geili."
But recently so the word "geili" is widespread across China now, probably because a re-dubbing of a Japanese animation is very popular. Most people think it depicted the plot vividly. So "geili" is now everywhere.
Some people, with nothing better to do, took the chance to translate it into English. Since "geili" sounds like "geli" with the "e" reduced to schwa, they invented the word "geli." And Chinese does not have part of speech, so it can be a noun, a verb, an adjective or adverb at the same time. To fit into different part of speech, they created "gelivabe" the adjective, and "gelivability" the noun. Accordingly, there came "ungelivable" and "ungelivability."