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Found one definition

1.                 From The Collaborative International Dictionary of English v.0.48:
                   
   
   
                   
                     
   Backslide \Back"slide"\ (b[a^]k"sl[imac]d"; 277), v. i. [imp.
      Backslid; p. p. Backslidden, Backslid; p. pr. & vb. n.
      Backsliding.] [Back, adv. + slide.]
      To slide back; to fall away; esp. to abandon gradually the
      faith and practice of a religion that has been professed.
      [1913 Webster]