tt

(noun) (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions. Synonyms: terrestrial time, TT, terrestrial dynamical time, TDT, ephemeris time.

(noun) a republic in the western central Pacific Ocean in association with the United States. Synonyms: Palau, Republic of Palau, TT.

(noun) a country scattered over Micronesia with a constitutional government in free association with the United States; achieved independence in 1986. Synonyms: Micronesia, Federated States of Micronesia, TT.