The Collaborative International Dictionary of English v.0.48:

Blush \Blush\, v. t.
   1. To suffuse with a blush; to redden; to make roseate.
      [Obs.]
      [1913 Webster]

            To blush and beautify the cheek again. --Shak.
      [1913 Webster]

   2. To express or make known by blushing.
      [1913 Webster]

            I'll blush you thanks.                --Shak.
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The Collaborative International Dictionary of English v.0.48:

Blush \Blush\ (bl[u^]sh) v. i. [imp. & p. p. Blushed
   (bl[u^]sht); p. pr. & vb. n. Blushing.] [OE. bluschen to
   shine, look, turn red, AS. blyscan to glow; akin to blysa a
   torch, [=a]bl[=y]sian to blush, D. blozen, Dan. blusse to
   blaze, blush.]
   [1913 Webster]
   1. To become suffused with red in the cheeks, as from a sense
      of shame, modesty, or confusion; to become red from such
      cause, as the cheeks or face.
      [1913 Webster]

            To the nuptial bower
            I led her blushing like the morn.     --Milton.
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            In the presence of the shameless and unblushing, the
            young offender is ashamed to blush.   --Buckminster.
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            He would stroke
            The head of modest and ingenuous worth,
            That blushed at its own praise.       --Cowper.
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   2. To grow red; to have a red or rosy color.
      [1913 Webster]

            The sun of heaven, methought, was loth to set,
            But stayed, and made the western welkin blush.
                                                  --Shak.
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   3. To have a warm and delicate color, as some roses and other
      flowers.
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            Full many a flower is born to blush unseen. --T.
                                                  Gray.
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The Collaborative International Dictionary of English v.0.48:

Blush \Blush\, n.
   1. A suffusion of the cheeks or face with red, as from a
      sense of shame, confusion, or modesty.
      [1913 Webster]

            The rosy blush of love.               --Trumbull.
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   2. A red or reddish color; a rosy tint.
      [1913 Webster]

            Light's last blushes tinged the distant hills.
                                                  --Lyttleton.
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   At first blush, or At the first blush, at the first
      appearance or view. "At the first blush, we thought they
      had been ships come from France." --Hakluyt.

   Note: This phrase is used now more of ideas, opinions, etc.,
         than of material things. "All purely identical
         propositions, obviously, and at first blush, appear,"
         etc. --Locke.

   To put to the blush, to cause to blush with shame; to put
      to shame.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blush
    n 1: a rosy color (especially in the cheeks) taken as a sign of
         good health [syn: bloom, blush, flush, rosiness]
    2: sudden reddening of the face (as from embarrassment or guilt
       or shame or modesty) [syn: blush, flush]
    v 1: turn red, as if in embarrassment or shame; "The girl
         blushed when a young man whistled as she walked by" [syn:
         blush, crimson, flush, redden]
    2: become rosy or reddish; "her cheeks blushed in the cold
       winter air"

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "blush":
   be guilty, blanch, bloom, blossom, blushing, change color, color,
   color up, coloring, crimson, crimsoning, darken, fieriness, flame,
   flush, flushing, glow, grow red, healthy glow, hectic,
   hectic flush, incandescence, look black, look guilty, mantle,
   mantling, pale, pink, pudency, pudicity, redden, reddening,
   redness, rose, rosiness, rouge, rubefacient, rubescence,
   rufescence, squirm with self-consciousness, stammer, suffusion,
   turn color, turn pale, turn red, warm color, warmth,
   warmth of color, whiten, whiteness