short pants vs trunks

short pants and trunks both are nouns.

Word	Noun	Adjective	Verb	Adverb
short pants	Yes	No	No	No
trunks	Yes	No	No	No

As nouns, short pants and trunks are synonyms defined as:

short pants and trunks: (used in the plural) trousers that end at or above the knee

Other synonyms of short pants include shorts.

short pants (noun)	trunks (noun)
(used in the plural) trousers that end at or above the knee	(used in the plural) trousers that end at or above the knee