Definition - The immediate, involuntary repeating of words or phrases just spoken by others.
Note: In educational psychology the term denotes "the repeating of words and phrases by children who are learning to speak."

Example -

Dave: "Hi Bob."
Bob: "Hi Bob."
Dave: "I'm not Bob. I'm Dave. You're Bob!"
Bob: "I'm not Bob. I'm Dave. You're Bob!"
Dave: "Shut up! Bob!"
Bob: "Shut up! Bob!"

Etymology -
The word was coined by combining the word echo (from the Greek ekhe, sound) with the Greek-derived suffix lalia, a speaking.

Oxford English Dictionary -
The word's first OED citation is from 1885:
"Periphrastic forms of speech and the recurring or barrel-organ utterances, constituting what is known as echolalia."
(Buck's Handbook Med. Sci. I. 290/1)

Please comment