1. Godan verb with 'ru' ending, Intransitive verb

   to reach an extreme; to reach a limit; to terminate; to come to an end

   下品極まる盛り場に通いつける。

2. Auxiliary verb, Noun or verb acting prenominally, Godan verb with 'ru' ending

   extremely

   after adjectival noun. e.g. 退屈極まる話

3. Godan verb with 'ru' ending, Intransitive verb

   to be stuck; to be in a dilemma; to be at a loss

   esp. 窮まる. occ. 谷まる

4. to be decided; to be settled

Also written 窮まる【きわまる】kiwamaru