Envelope \En"vel*ope\ (?; 277), Envelop \En*vel"op\ (?; 277), n. [F. enveloppe.]

1. That which envelops, wraps up, encases, or surrounds; a wrapper; an inclosing cover; esp., the cover or wrapper of a document, as of a letter.

2. (Astron.) The nebulous covering of the head or nucleus of a comet; -- called also coma.

3. (Fort.) A work of earth, in the form of a single parapet or of a small rampart. It is sometimes raised in the ditch and sometimes beyond it. --Wilhelm.

4. (Geom.) A curve or surface which is tangent to each member of a system of curves or surfaces, the form and position of the members of the system being allowed to vary according to some continuous law. Thus, any curve is the envelope of its tangents.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Coma \Co"ma\ (k[=o]"m[.a]), n. [NL., fr. Gr. kw^ma lethargy, fr. koima^n to put to sleep. See Cemetery.]

A state of profound insensibility from which it is difficult or impossible to rouse a person. See Carus.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Coma \Co"ma\, n. [L., hair, fr. Gr. ko`mh.]

1. (Astron.) The envelope of a comet; a nebulous covering, which surrounds the nucleus or body of a comet.

2. (Bot.) A tuft or bunch, -- as the assemblage of branches forming the head of a tree; or a cluster of bracts when empty and terminating the inflorescence of a plant; or a tuft of long hairs on certain seeds.

Coma Berenices[L.]

(Astron.), a small constellation north of Virgo; -- called also Berenice's Hair.

Source: Webster's Revised Unabridged Dictionary (1913)