Definition of spitballs:
(v) :
(figurative, originally US) To brainstorm ideas.
(n) :
A balled-up piece of paper, moistened with saliva (by chewing) and shot through a drinking straw.
(n) :
(baseball) A pitch of a baseball that has been partly covered with saliva, illegal at most levels.
(v) :
(baseball) To moisten the ball with saliva before pitching it.