[Sashimister]

When I answered the OP's question late last night, I actually had a premonition that this was going to be at least a 2-page thread because I knew no one was going to find きめ in his dictionary.

As has already been answered, きめ is the Kanto pronunciation of きも（きもい）. きもい itself is the slang word for 気持ち悪い, and when a new slang word gets heavily used for over a period of time (several years), it gets treated like a dictionary word in the sense that its regional pronunciations can start getting formed. In other words, きめ is the colloquial pronunciation of what's already a slang word　きもい.

In Kanto, adjective ending in "oi" and "ai" are often pronounced with "ee"(e-).
Good examples would be:
すごい　＞　すげー <-- this should explain きめー
うまい　＞　うめー

So it's only natural for the Kanto kids to pronounce きもい as きめー, and further opt for きめ for speedier pronunciation and texting.
＿＿＿＿＿＿＿＿

Someone stated that we went from 気持ち悪い　to きめ　"directly", but that's just plain wrong. There have been steps in between.