doing
something subjectively meaningless, i.e.
something that is objectively useful to everyone, including yourself, except the person who uses this phrase on you, who defines your activity as
useless and subjective only to themselves).
mother: Adam, go help your
father in the yard, if I
may interrupt you. All you've been doing to day in playing Minecraft.
Adam: okay, I'll go help dad, but remember that the
purpose, of playing Minecraft, I mean the actual game, is subjectively meaningless to youm, since everybody objectively defines it as useful except for you. (Adam goes off to help his dad).