The Collaborative International Dictionary of English v.0.48:

Ambush \Am"bush\ ([a^]m"b[oo^]sh), n. [F. emb[^u]che, fr. the
   verb. See Ambush, v. t.]
   1. A disposition or arrangement of troops for attacking an
      enemy unexpectedly from a concealed station. Hence: Unseen
      peril; a device to entrap; a snare.
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            Heaven, whose high walls fear no assault or siege
            Or ambush from the deep.              --Milton.
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   2. A concealed station, where troops or enemies lie in wait
      to attack by surprise.
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            Bold in close ambush, base in open field. --Dryden.
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   3. The troops posted in a concealed place, for attacking by
      surprise; liers in wait. [Obs.]
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            The ambush arose quickly out of their place. --Josh.
                                                  viii. 19.
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   To lay an ambush, to post a force in ambush.
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