Definition of lulls:
(n) :
A period of rest or soothing.
(n) :
A period of reduced activity; a respite.
(v) :
(transitive) To cause to rest by soothing influences; to compose; to calm
(v) :
(intransitive) To become gradually calm; to subside; to cease or abate.
(n) :
(nautical) A period without waves or wind.
(n) :
(surfing) An extended pause between sets of waves.