pulling vs tug

pulling and tug both are nouns.

Word	Noun	Adjective	Verb	Adverb
pulling	Yes	No	No	No
tug	Yes	No	Yes	No

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

pulling: the act of pulling; applying force to move something toward or with you
tug: a sudden abrupt pull

Other hyponyms of pulling include drag, draw, haul, haulage, jerk, draft, draught, drawing, deracination, excision, extirpation, pluck, traction.

pulling (noun)	tug (noun)
the act of pulling; applying force to move something toward or with you	a sudden abrupt pull
	a powerful small boat designed to pull or push larger ships

pulling (verb)	tug (verb)
	struggle in opposition
	pull hard
	pull or strain hard at
	move by pulling hard
	carry with difficulty
	tow (a vessel) with a tug
	strive and make an effort to reach a goal