1
adjective (keiyoushi)
inexcusable;unjustifiable;unpardonable
2
adjective (keiyoushi)
sorry;remorseful;apologetic;conscience-stricken;contrite
待たせてすまなかったな。
I am sorry to have kept you waiting.
3
interjection (kandoushi)
excuse me;(I'm) sorry;thank you
See also:
済みません (すみません)
すまないが今僕、手がいっぱいなのだ。
Excuse me, but I'm tied up now.