peridot UK /ˈpɛɹ.ɪ.dɒt/US /ˈpɛɹ.ɪ.dɑt/ noun2 •A transparent olive green form of olivine, used as a gem.Gem-quality olivine is known as peridot, which has a subtle green light all its own. — 2004 •A yellow-green color, like that of the peridot. formsperidots