to perform a task that requires meaningful expenditure of energy and time but yields no conceivable benefits; may be done unwittingly, in which case this phrase may be used to gently admonish the hearer of the futility of his efforts, redirecting him to more productive tasks; this activity may also be done to provide the appearance of productivity to outsiders, who will not investigate further and thus uncover the truth; rel., water the grass in a thunderstorm