The Collaborative International Dictionary of English v.0.48:

Dismount \Dis*mount"\, v. i. [imp. & p. p. Dismounted; p. pr.
   & vb. n. Dismounting.] [Pref. dis- + mount: cf. OF.
   desmonter, F. d['e]monter.]
   1. To come down; to descend. [Poetic]
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            But now the bright sun ginneth to dismount.
                                                  --Spenser.
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   2. To alight from a horse; to descend or get off, as a rider
      from his beast; as, the troops dismounted.
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