The Collaborative International Dictionary of English v.0.48:

Becalm \Be*calm"\, v. t. [imp. & p. p. Becalmed (?); p. pr. &
   vb. n. Becalming.]
   1. To render calm or quiet; to calm; to still; to appease.
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            Soft whispering airs . . . becalm the mind.
                                                  --Philips.
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   2. To keep from motion, or stop the progress of, by the
      stilling of the wind; as, the fleet was becalmed.
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