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.
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   2. To express or make known by blushing.
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            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.
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            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.
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            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.
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            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"