velum

noun9

1. •
   A thin membrane resembling a veil or curtain.
2. •
   The soft palate.
3. •
   A thin membrane partially covering the cluster of sporangia near the leaf base in quillworts and their extinct relatives.
4. •
   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.
5. •
   A locomotory and feeding organ provided with cilia found in the larval stage of bivalves.
6. •
   An annular membrane, typically bordering a cavity, especially in certain molluscs, medusae, and other invertebrates.
7. •
   A delicate membrane found on certain protists.
8. •
   An accessory cloud resembling a veil extending over a large distance; normally associated with cumulus and cumulonimbus.
9. •
   a thin coating or film of mucus or phlegm.