verb.
To free from misconception, deception or error.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
verb.
free from deception or illusion
Word Usage
"Their avowed object was to present a petition personally to the Prince Regent, that they might "undeceive" him; as if such a thing were possible, or, being possible, would be of the slightest service."