velum

Etymology

Borrowed from Latin vēlum (“a cloth, covering, awning, curtain, veil”). Doublet of veil.

noun

1. a thin membrane resembling a veil or curtain, such as:
   1. (anatomy) the soft palate
   2. (botany) a thin membrane partially covering the cluster of sporangia near the leaf base in quillworts and their extinct relatives
   3. (mycology) a veil-like membrane of immature mushrooms extending from the margin of the cap to the stem and is torn by growth, to reveal the gills
   4. (malacology) a locomotory and feeding organ provided with cilia found in the larval stage of bivalves
   5. (zoology) a annular membrane, typically bordering a cavity, especially in certain molluscs, medusae, and other invertebrates
   6. a delicate membrane found on certain protists
2. (meteorology) an accessory cloud resembling a veil extending over a large distance; normally associated with cumulus and cumulonimbus