ambush vs surprise attack

ambush and surprise attack both are nouns.

Word	Noun	Adjective	Verb	Adverb
ambush	Yes	No	Yes	No
surprise attack	Yes	No	No	No

As nouns, surprise attack is a hypernym of ambush; that is, surprise attack is a word with a broader meaning than ambush:

ambush: the act of concealing yourself and lying in wait to attack by surprise
surprise attack: an attack without warning

Other hypernyms of ambush include coup de main.

ambush (noun)	surprise attack (noun)
the act of concealing yourself and lying in wait to attack by surprise	an attack without warning

ambush (verb)	surprise attack (verb)
wait in hiding to attack
hunt (quarry) by stalking and ambushing