Definition of "kibitzer"

"Don't be a kibitzer!" Grampa snapped. "When I need help, I'll ask for it. No dad-blamed machine is gonna outthink Grampa!" He snorted indignantly.

1956 January, James E. Gunn, “The Gravity Business”, in Galaxy‎

Neither good nor evil exactly, he is the ultimate catalyst or kibitzer, a blue-note howl of pain and laughter such as Charlie Parker might have blown.

1971 November 5, Anatole Broyard, “Updike Goes All Out at Last”, in The New York Times‎, Books of The Times