The act of philosophizing while masturbating. When one starts to masturbate, their mind may drift away from the sexual thoughts of how their crush, girlfriend, fiance, or whatever pushes her ass up in the air while she reads the newspaper off the table (she stands up when she does it, and it's not like you're complaining), to more pressing matters, such as the meaning of life, the universe, and who thought to make yogurt drinkable. When you delve deep into these thoughts, you are philosofapping. Most people have philosofapped before, but haven't a term for it. This is that term.
Derek began philosofap, juggling in his mind whether or not it is justified to mail shit bricks to telemarketers.