"Nut:
1. (Science: botany) A dry one-seeded fruit which is indehiscent (i.e., it does not split open along a definite seam at maturity). Among the true nuts are the acorn, chestnut, hazelnut, beech, filbert, etc). Others that are not botanically true nuts are the peanut, cashew, coconut, litchi, pistachio, almond and the walnut."
That's as defined by Biology Online (
http://www.biology-online.org/...)
Interesting that walnuts, almonds, and even coconuts aren't nuts.
