1 [intransitive and transitive]
if a container, pipe, roof etc leaks, or if it leaks gas, liquid etc, there is a small hole or crack in it that lets gas or liquid flow through:
The roof is leaking.
A tanker is leaking oil off the coast of Scotland.
2 [intransitive always + adverb/preposition]
if a gas or liquid leaks somewhere, it gets through a hole in something [= seep]
Sea water was leaking into the batteries which powered the electric motors.
to deliberately give secret information to a newspaper, television company etc:
The report's findings had been leaked.
leak something to somebody
civil servants who leak information to the press
leak outphrasal verb
No sooner had the news leaked out than my telephone started ringing.