godan verb (-ru), intransitive verb
Almost exclusively used in the negative potential form たまらない (堪らない) meaning 'unbearable' or 'irresistible'. The plain form たまる is rare and often emphatic, appearing in set phrases like たまるか ('as if I could bear it!').
See also: 堪らない
こんなに暑くてはたまらない。
It's unbearably hot like this.
As if I could stand losing!