The Collaborative International Dictionary of English v.0.48:

Curb \Curb\ (k[^u]rb), v. t. [imp. & p. p. Curbed (k[^u]rbd);
   p. pr. & vb. n. Curbing.] [F. courber to bend, curve,
   L.curvare, fr. curvus bent, curved; cf. Gr. kyrto`s curved.
   Cf. Curve.]
   1. To bend or curve. [Obs.]
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            Crooked and curbed lines.             --Holland.
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   2. To guide and manage, or restrain, as with a curb; to bend
      to one's will; to subject; to subdue; to restrain; to
      confine; to keep in check.
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            Part wield their arms, part curb the foaming steed.
                                                  --Milton.
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            Where pinching want must curb thy warm desires.
                                                  --Prior.
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   3. To furnish with a curb, as a well; also, to restrain by a
      curb, as a bank of earth.
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WordNet (r) 3.0 (2006):

curbing
    n 1: an edge between a sidewalk and a roadway consisting of a
         line of curbstones (usually forming part of a gutter) [syn:
         curb, curbing, kerb]