The Collaborative International Dictionary of English v.0.48:

Leaky \Leak"y\, a. [Compar. Leakier; superl. Leakiest.]
   1. Permitting water or other fluid to leak in or out; as, a
      leaky roof or cask; a leaky faucet.
      [1913 Webster]

   2. Apt to disclose secrets; tattling; not close. [Colloq.]
      [1913 Webster]

   3. (Genetics) Retaining some function; not completely
      inactivating the gene; as, substitution mutations are
      sometimes leaky; -- of mutations.
      [PJC]

WordNet (r) 3.0 (2006):

leaky
    adj 1: permitting the unwanted passage of fluids or gases ; "a
           leaky roof"; "a leaky defense system" [ant: tight]
    2: used informally; unable to retain urine
    3: prone to communicate confidential information [syn:
       blabbermouthed, leaky, talebearing(a), tattling(a)]