Naiad (nāyăd; 277), n. [L. naias, -adis, naïs, -idis, a water nymph, Gr nai:as, nai:s, fr. naein to flow: cf. F. naïade. Cf. Naid.] 1. (Myth.) A water nymph; one of the lower female divinities, fabled to preside over some body of fresh water, as a lake, river, brook, or fountain.
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2. (Zoöl.) Any species of a tribe (Naiades) of freshwater bivalves, including Unio, Anodonta, and numerous allied genera; a river mussel.
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3. (Zoöl) One of a group of butterflies. See Nymph.
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4. (Bot.) Any plant of the order Naiadaceæ, such as eelgrass, pondweed, etc.
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