pursuit vs trailing

pursuit and trailing both are nouns.

Word	Noun	Adjective	Verb	Adverb
pursuit	Yes	No	No	No
trailing	Yes	No	No	No

As nouns, trailing is a hyponym of pursuit; that is, trailing is a word with a more specific, narrower meaning than pursuit:

pursuit: the act of pursuing in an effort to overtake or capture
trailing: the pursuit (of a person or animal) by following tracks or marks they left behind

Other hyponyms of pursuit include tracking, shadowing, tailing, stalk, stalking.

pursuit (noun)	trailing (noun)
the act of pursuing in an effort to overtake or capture	the pursuit (of a person or animal) by following tracks or marks they left behind
a diversion that occupies one's time and thoughts (usually pleasantly)
an auxiliary activity
a search for an alternative that meets cognitive criteria