bay at the moon
To make appeals in vain. Good luck talking to the principal, but I think you'll just be baying at the moon—I doubt you'll get a better grade.
bay at the moon
or howl at the moon
LITERARYIf you bay at the moon or howl at the moon, you waste your time and energy trying to do something which is impossible or trying to get something which you cannot have. You're looking for the perfect man and he doesn't exist. You're baying at the moon.
bay at the moon
clamour or make an outcry to no effect. The barking of dogs at a full moon has been a metaphor for futile activity since the mid 17th century.