The Collaborative International Dictionary of English v.0.48:

Clamber \Clam"ber\, v. i. [imp. & p. p. Clambered; p. pr. &
   vb. n. Clambering.] [OE clambren, clameren, to heap
   together, climb; akin to Icel. klambra to clamp, G. klammern.
   Cf. Clamp, Climb.]
   To climb with difficulty, or with hands and feet; -- also
   used figuratively.
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         The narrow street that clambered toward the mill.
                                                  --Tennyson.
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The Collaborative International Dictionary of English v.0.48:

Clamber \Clam"ber\, n.
   The act of clambering. --T. Moore.
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The Collaborative International Dictionary of English v.0.48:

Clamber \Clam"ber\, v. t.
   To ascend by climbing with difficulty.
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         Clambering the walls to eye him.         --Shak.
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WordNet (r) 3.0 (2006):

clamber
    n 1: an awkward climb; "reaching the crest was a real clamber"
    v 1: climb awkwardly, as if by scrambling [syn: clamber,
         scramble, shin, shinny, skin, struggle,
         sputter]