nail-biting \ˈ ̷ ̷ˌ ̷ ̷ ̷ ̷\noun 1. a.: habitual biting at the fingernails usually being symptomatic of emotional tensions and frustrations b.: an act or instance of this behavior 2.: a hopelessly or helplessly frustrated condition or activity < their critical work has become largely a kind of ethical nail-biting — S.E.Hyman >