What does lump mean?

A "lump" is a defined physical mass, and is applied to : * a small agglomeration or collection, as "a lump of coal" * small collections within a softer material, as "a lumpy mattress" * (medical) a smaller mass within soft tissue agglomeration, or cyst * (medical) an outgrowth caused by growth or injury, as "a lump on the head" (also, bump)