dirt bike vs trail bike

dirt bike and trail bike both are nouns.

Word	Noun	Adjective	Verb	Adverb
dirt bike	Yes	No	No	No
trail bike	Yes	No	No	No

As nouns, dirt bike and trail bike are synonyms defined as:

dirt bike and trail bike: a lightweight motorcycle equipped with rugged tires and suspension; an off-road motorcycle designed for riding cross country or over unpaved ground

Other synonyms of dirt bike include scrambler.

dirt bike (noun)	trail bike (noun)
a lightweight motorcycle equipped with rugged tires and suspension; an off-road motorcycle designed for riding cross country or over unpaved ground	a lightweight motorcycle equipped with rugged tires and suspension; an off-road motorcycle designed for riding cross country or over unpaved ground