A type of motion (gati);
when any person starts from some place with an intention to reach a destination, before he reaches the ultimate destination, through every step, he covers some distance towards his goal; by dividing the intermediate distance in several sub-destinations, the movement through which such sub-destinations are covered is called Tatagati.
yaṃ grāmāṃ sanniveśaṃ vā prati pratisthito devadattādistaṃ grāmādikaṃ yāvaddyāpi na prāpnoti tāvadantarāpathi ekaikasmin padanyāse tattaddeśāntaraprāptilakṣaṇā gatirastīti tatagatiḥ.
(Prajñā 16.22 Vṛ Pa 328)