immensity n. + Add to list UK //ɪmˈɛnsɪti// im·men·si·ty SynonymsEtymology Synonyms enormousnessgrandnessgreatnessimmensenesssizeablenessvastnesswidenessOrigin From Middle French immensité, equivalent to immense + -ity. Idioms1 entry01temple of immensityThe universe or the complete overhead expanse of the heavens, especially as conceived as an object of religious reverence.