ˈenvələup n. 1 a folded
paper container, usu.
with a sealable
flap,
for a
letter etc. 2 a
wrapper or
covering. 3
the structure within a
balloon or
airship containing the
gas. 4 the
outer metal or
glass housing of a
vacuum tube,
electric light, etc. 5 Electr. a
curve joining the
successive peaks of a modulated
wave. 6
Bot.
any enveloping structure
esp. the
calyx or
corolla (or both). 7
Math. a line or curve
tangent to
each line or curve of a
given family. [F enveloppe (as ENVELOP)]