half hourEnglishOxford New American Dictionaryhalf hour /ˌhaf ˈou(ə)r, ˌhæf ˈaʊ(ə)r/ ▸ noun (also half an hour) a period of thirty minutes: a slide show presented every half hour. ▪ a point in time thirty minutes after any full hour of the clock: the library clock struck the half hour. – DERIVATIVES half-hourly /ˈhaf ˌou(ə)rlē, ˈhæf ˌaʊ(ə)rli/ adjective & adverb