smasher vs megahit

smasher and megahit both are nouns.

Word	Noun	Adjective	Verb	Adverb
smasher	Yes	No	No	No
megahit	Yes	No	No	No

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

smasher: a conspicuous success
megahit: an unusually successful hit with widespread popularity and huge sales (especially a movie or play or recording or novel)

Other hyponyms of smasher include blockbuster, smash hit, sleeper.

smasher (noun)	megahit (noun)
a conspicuous success	an unusually successful hit with widespread popularity and huge sales (especially a movie or play or recording or novel)
a very attractive or seductive looking woman
a person who smashes something