From 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]
From 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)]