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 ]
n. One who backslides. [ 1913 Webster ]