Source : Webster's Revised Unabridged Dictionary (1913)

Sinful \Sin"ful\, a. [AAS. synfull.]
   Tainted with, or full of, sin; wicked; iniquitous; criminal;
   unholy; as, sinful men; sinful thoughts. --Piers Plowman.

         Ah sinful nation, a people laden with iniquity. --Isa.
                                                  i. 4.
   -- {Sin"ful*ly}, adv. -- {Sin"ful*ness}, n.