The Collaborative International Dictionary of English v.0.48:
Grave \Grave\, a. [Compar. Graver (gr[=a]v"[~e]r); superl.
Gravest.] [F., fr. L. gravis heavy; cf. It. & Sp. grave
heavy, grave. See Grief.]
1. Of great weight; heavy; ponderous. [Obs.]
His shield grave and great. --Chapman.
2. Of importance; momentous; weighty; influential; sedate;
serious; -- said of character, relations, etc.; as, grave
deportment, character, influence, etc.
Most potent, grave, and reverend seigniors. --Shak.
A grave and prudent law, full of moral equity.
3. Not light or gay; solemn; sober; plain; as, a grave color;
a grave face.
(a) Not acute or sharp; low; deep; -- said of sound; as, a
grave note or key.
The thicker the cord or string, the more grave
is the note or tone. --Moore
(b) Slow and solemn in movement.
Grave accent. (Pron.) See the Note under Accent, n., 2.
Syn: Solemn; sober; serious; sage; staid; demure; thoughtful;
sedate; weighty; momentous; important.
Usage: Grave, Sober, Serious, Solemn. Sober supposes
the absence of all exhilaration of spirits, and is
opposed to gay or flighty; as, sober thought. Serious
implies considerateness or reflection, and is opposed
to jocose or sportive; as, serious and important
concerns. Grave denotes a state of mind, appearance,
etc., which results from the pressure of weighty
interests, and is opposed to hilarity of feeling or
vivacity of manner; as, a qrave remark; qrave attire.
Solemn is applied to a case in which gravity is
carried to its highest point; as, a solemn admonition;
a solemn promise.