Bioaccumulation, or bioconcentration, is the progressive increase in the amount of a substance in an organism or part of an organism that occurs because the rate of intake exceeds the organism's ability to remove the substance from the body. Bioaccumulation often correlates with lipophilicity.

Bioaccumulation potential is the ability of living organisms to concentrate a substance obtained either directly from the environment or
indirectly through its food.

Illustration of Bioaccumulation (from Washington State Dept of Health)