Definition of larks:
(n) :
Any of various small, singing passerine birds of the family Alaudidae.
(n) :
(by extension) One who wakes early; one who is up with the larks.
(n) :
Any of various similar-appearing birds, but usually ground-living, such as the meadowlark and titlark.
(n) :
A frolic or romp, some fun.
(n) :
A jolly or peppy person.
(n) :
A prank.