In peaches, plums, cherries, etc. Note that the accent is on the first syllable, nòcciolo; otherwise, nocciòlo is a hazelnut tree.
Take out the stone: togliere il nòcciolo or snocciolare.
It's also a small dogfish, palombo nocciolo, sometimes served in place of swordfish or in a cacciucco.
Images by: Christopher Bowns