Iiwake (言い訳): an excuse. Explaining after a failure that there was no other choice, in order to justify oneself. Iiwake suru na: no excuses. A common rebuke to someone who has failed.
Kuchigotae (口答え): talking back. Answering a parent, teacher or boss argumentatively. Herikutsu (屁理屈): fart logic. Forced reasoning made to fit.
Chikara busoku (力不足): lack of ability. Used of oneself in apologies, as in watakushi no chikara busoku de, through my lack of ability.