The Collaborative International Dictionary of English v.0.48:

Horrent \Hor"rent\, a. [L. horrens, p. pr. of horrere to
   bristle. See Horror.]
   Standing erect, as bristles; covered with bristling points;
   bristled; bristling.
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         Rough and horrent with figures in strong relief. --De
   Quincey.
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         With bright emblazonry and horrent arms. --Milton.
   [1913 Webster]