Velum

From Latin velum ("veil, sail").

Full definition of velum

(plural vela)

(anatomy) The soft palate.
(botany) A thin membrane partially covering the cluster of sporangia near the leaf base in quillworts and their extinct relatives.
(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.
(malacology) A locomotory and feeding organ provided with cilia found in the larval stage of bivalves.
(zoology) A circular membrane round the cap of medusa.
A delicate membrane found on certain protists.

(meteorology) An accessory cloud resembling a veil extending over a large distance. Normally associated with cumulus and cumulonimbus.