The Collaborative International Dictionary of English v.0.48:

Staid \Staid\ (st[=a]d),
   imp. & p. p. of Stay.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Staid \Staid\, a. [From Stay to stop.]
   Sober; grave; steady; sedate; composed; regular; not wild,
   volatile, flighty, or fanciful. "Sober and staid persons."
   --Addison.
   [1913 Webster]

         O'erlaid with black, staid Wisdom's hue. --Milton.
   [1913 Webster]

   Syn: Sober; grave; steady; steadfast; composed; regular;
        sedate.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stay \Stay\ (st[=a]), v. t. [imp. & p. p. Stayed (st[=a]d) or
   Staid (st[=a]d); p. pr. & vb. n. Staying.] [OF. estayer,
   F. ['e]tayer to prop, fr. OF. estai, F. ['e]tai, a prop,
   probably fr. OD. stade, staeye, a prop, akin to E. stead; or
   cf. stay a rope to support a mast. Cf. Staid, a., Stay,
   v. i.]
   1. To stop from motion or falling; to prop; to fix firmly; to
      hold up; to support.
      [1913 Webster]

            Aaron and Hur stayed up his hands, the one on the
            one side, and the other on the other side. --Ex.
                                                  xvii. 12.
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            Sallows and reeds . . . for vineyards useful found
            To stay thy vines.                    --Dryden.
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   2. To support from sinking; to sustain with strength; to
      satisfy in part or for the time.
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            He has devoured a whole loaf of bread and butter,
            and it has not staid his stomach for a minute. --Sir
                                                  W. Scott.
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   3. To bear up under; to endure; to support; to resist
      successfully.
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            She will not stay the siege of loving terms,
            Nor bide the encounter of assailing eyes. --Shak.
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   4. To hold from proceeding; to withhold; to restrain; to
      stop; to hold.
      [1913 Webster]

            Him backward overthrew and down him stayed
            With their rude hands and grisly grapplement.
                                                  --Spenser.
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            All that may stay their minds from thinking that
            true which they heartily wish were false. --Hooker.
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   5. To hinder; to delay; to detain; to keep back.
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            Your ships are stayed at Venice.      --Shak.
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            This business staid me in London almost a week.
                                                  --Evelyn.
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            I was willing to stay my reader on an argument that
            appeared to me new.                   --Locke.
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   6. To remain for the purpose of; to wait for. "I stay dinner
      there." --Shak.
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   7. To cause to cease; to put an end to.
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            Stay your strife.                     --Shak.
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            For flattering planets seemed to say
            This child should ills of ages stay.  --Emerson.
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   8. (Engin.) To fasten or secure with stays; as, to stay a
      flat sheet in a steam boiler.
      [1913 Webster]

   9. (Naut.) To tack, as a vessel, so that the other side of
      the vessel shall be presented to the wind.
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   To stay a mast (Naut.), to incline it forward or aft, or to
      one side, by the stays and backstays.
      [1913 Webster]

WordNet (r) 3.0 (2006):

staid
    adj 1: characterized by dignity and propriety [syn: sedate,
           staid]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "staid":
   arid, barren, calm, collected, composed, cool, decorous, demure,
   dignified, dry, dull, earnest, earthbound, formal, frowning, grave,
   grim, grim-faced, grim-visaged, infecund, infertile, literal,
   long-faced, moderate, mundane, no-nonsense, priggish, prim,
   prosaic, prosing, prosy, quiet, restrained, rigid, sedate, serious,
   serious-minded, smug, sober, sober-minded, sobersided, solemn,
   somber, starchy, stiff, stolid, stone-faced, straight-faced,
   stuffy, temperate, thoughtful, unfanciful, unideal, unimaginative,
   uninspired, uninventive, unoriginal, unpoetic, unromantic,
   unromanticized, unsmiling, weighty