A partsong in which voices follow each other; one voice starts and others join in one after another until all are singing different parts of the song at the same time WordNet 3.0 & Open English WordNet

A round is a musical composition, a limited type of canon, in which a minimum of three voices sing exactly the same melody at the unison, but with each voice beginning at different times so that different parts of the melody coincide in the different voices, but nevertheless fit harmoniously together. Wikipedia

A type of musical composition Wikipedia Disambiguation

Musical composition type Wikidata

Song with each subset starting at a different time. Wiktionary (translation)

A song that is sung by groups of people with each subset of people starting at a different time. Wiktionary

A song whose parts are sung in succession; a catch; a round. Wiktionary