From The Collaborative International Dictionary of English v.0.48 [gcide]:
Cowardliness \Cow"ard*li*ness\ (-l?-n?s), n.
Cowardice.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
cowardliness
n 1: the trait of lacking courage [syn: cowardice,
cowardliness] [ant: braveness, bravery, courage,
courageousness]