The Collaborative International Dictionary of English v.0.48:

Cowardliness \Cow"ard*li*ness\ (-l?-n?s), n.
   Cowardice.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cowardliness
    n 1: the trait of lacking courage [syn: cowardice,
         cowardliness] [ant: braveness, bravery, courage,
         courageousness]