Tusit, Tusita

sk तुष्ट tuṣṭa, “(becoming) pleased”, "contented" | pl tusit, "satisfaction", "felicity"; tusitā, "those who are satisfied" | kh តុសិត chu'sit, "realm of the fourth level" | th ดุสิต dusit "fourth heaven" | ch 兜率天 dou leu tien "Tusita Heaven"

Tusit in Pali is the name of the fourth level of heavenly realm. Tusita refers to a a class of deva [Buddhist heavenly beings] who are 'satisfied' in the sensuous plane.

In Cambodian Theravada Buddhism, the name of the fourth level of the Kamavacarya Heaven, with King Sandosit as the presiding deity. Bodhisattvas, the Buddha Father, the Buddha Mother, and all other highly meritorious beings are often reborn and reside in this realm.

All the Supreme Bodhisattvas, and even the Metteya Buddha (future successor of Gautama Buddha) reside in the Tusit realm, which is itself a non-permanent level of pure felicity.

Source

Pali Dictionary
Chhuon Nath Dictionary
Didier Treutenaere, Bouddhisme et renaissance dans la Tradition Theravada, Paris, Soukha Ed., 2018, p. 101.