The term "lump it" means to not do something or forget about it. Lump it replaces the saying "fuck it." However, lumping it gives you the same satisfaction as if you did the task at hand, even if you didn't perform such an action. "Lump it" can be used as a noun, adjective and verb, such as; Lump it, Just lump it, lumping, lumped or simply lump. The use of the phrase will soon come naturally. I would explain the definition more but lump it.
Mike: "I have a paper due for class tomorrow."
James: "Just lump it bro."
Mike: "Good call man."
Zoie: "Wake up! You have class in 15 minutes!"
James: "Nah, I'm just gonna lump it."
Zoie: "James! Wake up!
James: "Baby, I said I'm lumping it."
Mike: "Imma be lumping it in my bed all day."
James: "Cool, watch me play Skate2."
Mike: "Alright, toss me a soda bro."
From the Idiom, "like it or lump it." Meaning to cope with a situation that is beyond one's control or design.
I failed my course. Guess I'll have to lump it.