hooter vs motor horn

hooter and motor horn both are nouns.

Word	Noun	Adjective	Verb	Adverb
hooter	Yes	No	No	No
motor horn	Yes	No	No	No

As nouns, hooter and motor horn are synonyms defined as:

hooter and motor horn: a device on an automobile for making a warning noise

Other synonyms of hooter include automobile horn, car horn, horn.

hooter (noun)	motor horn (noun)
nocturnal bird of prey with hawk-like beak and claws and large head with front-facing eyes	a device on an automobile for making a warning noise
a device on an automobile for making a warning noise
informal terms for the nose