Wordnet 3.0
NOUN (1)
1. 
 the condition of permitting leaks or leakage; 
- Example: "the leakiness of the roof"- Example: "the heart valve's leakiness"- Example: "the leakiness of the boat made it dangerous to use"
The Collaborative International Dictionary of English v.0.48:
Leakiness \Leak"i*ness\, n.
   The quality of being leaky.
   [1913 Webster]
WordNet (r) 3.0 (2006):
leakiness
    n 1: the condition of permitting leaks or leakage; "the
         leakiness of the roof"; "the heart valve's leakiness"; "the
         leakiness of the boat made it dangerous to use"