interjection

one of the traditional eight parts of speech, ¶2-2-10; i. are words usually contained in introverted utterances and often used to vent emotion, such as, Uch!, ¶3-1-4; single word variations of socially motivated expressions also belong to the class of i., such as, Hurrah!, ¶3-1-5, ¶3-1-6; exclamatory i. are sometimes called expletives