Source : Webster's Revised Unabridged Dictionary (1913)

Trustful \Trust"ful\, a.
   1. Full of trust; trusting.

   2. Worthy of trust; faithful; trusty; trustworthy. --
      {Trust"ful*ly},adv. -- {Trust"ful*ness}, n.

Source : WordNet®

trustfulness
     n : the trait of trusting; of believing in the honesty and
         reliability of others; "the experience destroyed his
         trust and personal dignity" [syn: {trust}, {trustingness}]
         [ant: {distrust}]