Meaningless work is work which does not accomplish or serve any conventional purpose. Meaningless work can consume your time, your energy, your money, while producing you nothing. You will not derive pleasure, at least physical pleasure, from it, nor will you get any other material reward from it. Walter DeMaria wrote in Ananthology (around 1960):
"Meaningless work is potentially the most abstract, concrete, individual, foolish, indeterminate, exactly determined, varied, important art-action-experience one can undertake today. This concept is not a joke. Try some meaningless work in the privacy of your own room. In fact, to be fully understood, meaningless work should be done alone or else it becomes entertainment for others and the reaction or lack of reaction of the art lover to the meaningless work can not honestly be felt."
Meaningless work can calm your senses, restore your spirit and clear your mind, allowing you to reach a state of true relaxation. No more deadlines to meet, no more targets to run towards. Personally, I have found meaningless work to be essential to my well-being. In fact, I do it more and more, while doing meaningful work less and less. Go out into the woods and sing.
See also: John Cage, La Monte Young, Fluxus, Indeterminate music