Lewis Short
hĭlărĭtas (noun F) : hilaris
* Cheerfulness, gayety, good-humor, joyousness, merriment, hilarity (class.): hilaritatem illam, qua hanc tristitiam temporum condiebamus, in perpetuum amisi,Cic. Att. 12, 40, 3; cf.: tristitia deductis, hilaritas remissis (superciliis) ostenditur,Quint. 11, 3, 79: hilaritate et lascivia,Cic. Fin. 2, 20, 65: itaque hilaritatis plenum judicium ac laetitiae fuit,id. de Or. 1, 57, 243: hilaritas illa nostra et suavitas,id. Fam. 9, 11, 1: erat in M. Druso adulescente singularis severitas, in C. Laelio multa hilaritas,id. Off. 1, 30, 108: in praecordiis praecipua hilaritatis sedes,Plin. 11, 37, 77, § 198: ut hilaritate enitescant (oculi),Quint. 11, 3, 75: ceterae hilaritates non implent pectus,Sen. Ep. 23, 3: cum diei permittit hilaritas,fineness, pleasantness,Col. 9, 14, 18: arboris, i. e. a fresh or lively appearance, Plin. 17, 16, 26, § 118.
Charlton T. Lewis, Charles Short, A Latin Dictionary