没齿难忘

hard to forget even after one's teeth fall out (idiom); to remember a benefactor as long as one lives / undying gratitude

(negative prefix for verbs) / have not / not

drowned / to end / to die / to inundate

(negative prefix for verbs) have not; not

difficult (to...) / problem / difficulty / difficult / not good

disaster / distress / to scold

to forget / to overlook / to neglect

unforgettable

tooth / CL:顆|颗[ke1]