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
Source: WordNetDoing so does not create another version of TAI; it is instead considered to be creating a better realisation of Terrestrial Time (TT). Source: Internet
Terrestrial Time is a theoretical uniform time scale, defined to provide continuity with the former Ephemeris Time (ET). Source: Internet