rattlesnake vs rattler

rattlesnake and rattler both are nouns.

Word	Noun	Adjective	Verb	Adverb
rattlesnake	Yes	No	No	No
rattler	Yes	No	No	No

As nouns, rattlesnake and rattler are synonyms defined as:

rattlesnake and rattler: pit viper with horny segments at the end of the tail that rattle when shaken

rattlesnake (noun)	rattler (noun)
pit viper with horny segments at the end of the tail that rattle when shaken	pit viper with horny segments at the end of the tail that rattle when shaken
	a railroad train consisting of freight cars