ambusher vs attacker

ambusher and attacker both are nouns.

Word	Noun	Adjective	Verb	Adverb
ambusher	Yes	No	No	No
attacker	Yes	No	No	No

As nouns, attacker is a hypernym of ambusher; that is, attacker is a word with a broader meaning than ambusher:

ambusher: an attacker who waits in a concealed position to launch a surprise attack
attacker: someone who attacks

Other hypernyms of ambusher include aggressor, assailant, assaulter.

ambusher (noun)	attacker (noun)
an attacker who waits in a concealed position to launch a surprise attack	someone who attacks