velum [`vē·lǝm] BIOLOGY A veil- or curtainlike membrane. INVERTEBRATE ZOOLOGY A swimming organ on the larva of certain marine gastropod mollusks that develops as a contractile ciliated collar-shaped ridge. Also known as veil. METEOROLOGY An accessory cloud veil of great horizontal extent draped over or penetrated by cumuliform clouds; velum occurs with cumulus and cumulonimbus. |