breathalyzer vs breathalyser

breathalyzer and breathalyser both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathalyzer	Yes	No	No	No
breathalyser	Yes	No	No	No

As nouns, breathalyzer and breathalyser are synonyms defined as:

breathalyzer and breathalyser: a device that measures chemicals (especially the alcohol content) in a person's expired breath

breathalyzer (noun)	breathalyser (noun)
a device that measures chemicals (especially the alcohol content) in a person's expired breath	a device that measures chemicals (especially the alcohol content) in a person's expired breath