outboard motor vs outboard

outboard motor and outboard both are nouns.

Word	Noun	Adjective	Verb	Adverb
outboard motor	Yes	No	No	No
outboard	Yes	Yes	No	No

As nouns, outboard motor and outboard are synonyms defined as:

outboard motor and outboard: internal-combustion engine that mounts at stern of small boat

outboard motor (noun)	outboard (noun)
internal-combustion engine that mounts at stern of small boat	internal-combustion engine that mounts at stern of small boat
	a motorboat with an outboard motor

outboard motor (adjective)	outboard (adjective)
	located away from the midline of a vessel or aircraft