(n.) One who meddles; one who interferes or busies himself with things in which he has no concern; an officious person; a busybody.

Dutch uncle Paul Pry Polonius admonisher adviser backseat driver busybody butt-in buttinsky confidant consultant counsel counselor expert guide instructor intermeddler kibitzer mentor monitor nestor orienter pragmatist preceptist prier pry quidnunc rubberneck snoop snooper teacher yenta