WordDictionary

Noun:

• Something that envelops; a wrapping
• A bag containing the lifting gas of a balloon or airship;title=The Chambers Dictionary |page=541 |quote=the gas-bag of a balloon or airship |publisher=Chambers Harrap Publishers Ltd |year=2000 |origyear=1998 |location=Edinburgh |isbn=0-550-14005-X fabric that encloses the gas-bags of an airshiptitle=The Oxford Illustrated Dictionary |page=281 |quote=|publisher=Oxford University Press |year=1976 |origyear=1975 |location=Great Britain
• A paper or cardboard wrapper used to enclose small, flat items, especially letters, for mailing.
• biology An enclosing structure or cover, such as a membrane.
• computing The information used for routing an email that is transmitted with the email but not part of its contents.
• electronics A curve that bounds another curve or set of curves, as the modulation envelope of an amplitude-modulated carrier wave in electronics.
• engineering The set of limitations within which a technological system can perform safely and effectively.
• geometry A mathematical curve, surface, or higher-dimensional object that is the tangent to a given family of lines, curves, surfaces, or higher-dimensional objects.
• music The shape of a sound, which may be controlled by a synthesizer or sampler.