semiautomatic vs side arm

semiautomatic and side arm both are nouns.

Word	Noun	Adjective	Verb	Adverb
semiautomatic	Yes	Yes	No	No
side arm	Yes	No	No	No

As nouns, side arm is a hypernym of semiautomatic; that is, side arm is a word with a broader meaning than semiautomatic:

semiautomatic: a pistol that is a semiautomatic firearm capable of loading and firing continuously
side arm: a firearm that is held and fired with one hand

Other hypernyms of semiautomatic include handgun, pistol, shooting iron, semiautomatic firearm.

semiautomatic (noun)	side arm (noun)
a pistol that is a semiautomatic firearm capable of loading and firing continuously	a firearm that is held and fired with one hand

semiautomatic (adjective)	side arm (adjective)
(of firearms) capable of automatic loading and firing continuously
partially automatic