double bass vs bass fiddle

double bass and bass fiddle both are nouns.

Word	Noun	Adjective	Verb	Adverb
double bass	Yes	No	No	No
bass fiddle	Yes	No	No	No

As nouns, double bass and bass fiddle are synonyms defined as:

double bass and bass fiddle: largest and lowest member of the violin family

Other synonyms of double bass include bass viol, bull fiddle, contrabass, string bass.

double bass (noun)	bass fiddle (noun)
largest and lowest member of the violin family	largest and lowest member of the violin family