A person who seemingly exists for the sole purpose of sharpening your wit. Analogous to a whetstone for knives. A witstone does not usually comprehend the subtleties of sarcasm, jokes, or human communication (especially the English language).
John said, "Everything I do makes this computer crash." When I replied that his breathing probably did not make the computer crash, he was confused. John is such a witstone.
by crosvenir March 18, 2011