Definition - Unintelligible speech that belongs to no known language.

Example -
Gdork flark proct?

Etymology -
The word was probably coined onomatopoeically in imitation of the sound of chatter; it was also probably modelled on the word jabber.

Oxford English Dictionary -
Its first citation is from circa 1554:
"What me thynke ye be clerkyshe For ye speake good gibbryshe."
( Interl. Youth Aijb)

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