The Collaborative International Dictionary of English v.0.48:

Holiness \Ho"li*ness\, n. [AS. h[=a]lignes.]
   1. The state or quality of being holy; perfect moral
      integrity or purity; freedom from sin; sanctity;
      innocence.
      [1913 Webster]

            Who is like thee, glorious in holiness! --Ex. xv.
                                                  11.
      [1913 Webster]

   2. The state of being hallowed, or consecrated to God or to
      his worship; sacredness.
      [1913 Webster]

            Israel was holiness unto the Lord.    --Jer.ii.3.
      [1913 Webster]

   His holiness, a title of the pope; -- formerly given also
      to Greek bishops and Greek emperors.

   Syn: Piety; devotion; godliness; sanctity; sacredness;
        righteousness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

holiness
    n 1: the quality of being holy [syn: holiness, sanctity,
         sanctitude] [ant: unholiness]