Douglas Harper's Etymology Dictionary
musical ensemble in which the bass line is carried or augmented by a player blowing on the open lip of a jug (n.), 1886, American English.
Wiktionary
n. (context music English) Especially in the U. S., a group of rustic musicians, specializing in bluegrass or folk music, whose instruments include empty jugs, bottles, and similar containers of various sizes which produce musical sounds when the player blows across the openings at the tops of their necks.
WordNet
n. a musical group that uses jugs and washboards and kazoos and other improvised instruments
Wikipedia
A jug band is a band employing a jug player and a mix of traditional and home-made instruments. These home-made instruments are ordinary objects adapted to or modified for making of sound, like the washtub bass, washboard, spoons, bones, stovepipe, and comb & tissue paper ( kazoo). The term jug band is loosely used in referring to ensembles that also incorporate home-made instruments but that are more accurately called skiffle bands, spasm bands, or juke (or jook) bands (see juke joint) because they are missing the required jug player.
Usage examples of "jug band".
The Duncan Brothers and Their Two-man Jug Band, he and Al had been, playing their own arrangements for two jugs of Bach and Mozart and Stravinsky.
Miller and Their Two-man Jug Band, he and Al Miller had been, playing their own arrangement for two jugs of Bach and Mozart and Stravinsky.
Actual fact, Blind Black was s'pose to be openin' for the Armadillo Jug Band.
But when the jug band found out it was Rosie, they insisted on openin' up for him.
A three-man jug band -- the Crab Suckers, a private joke no one else understands -- is on the raised platform at the front of the room, where the council usually sits when the monthly town meeting is in session.
At one point, possibly Wednesday, an entire jug band walked in- jug, washtub bass, washboard, guitar, harmonica and spoons- did a twenty-minute unamplified set, passed the hat, and then disappeared into the night again.