Synonyms for Tailing:

n.

tailing (noun)
following, shadowing.

v.

following (verb)
descending, resulting, succeeding, ensuing, lagging.
pursuing (verb)
Intending, dogging, Chasing, sleuthing, Endeavoring, hunting, questing, striving, tracking, seeking, Aiming, searching, Harrying, trailing, aspiring, stalking, undertaking, following, pursuing.

Other synonyms:

Other relevant words:
shadowing.