1. an extreme involvement or preoccupation with one object, idea, or pursuit, with inattention to other aspects of the environment. Compare sustained attention. See also Tellegen Absorption Scale.

2. the uptake of fluid and dissolved substances into a cell across the plasma membrane. For example, an administered drug moves through various biological membranes from its site of administration to its target organ. Absorption into the target organ is dependent on a number of factors, including the method of administration (e.g., oral, intravenous); the properties of the drug (e.g., molecular size, ability to cross lipid membranes); the amount of drug administered; and the characteristics or state of the individual (e.g., body mass, sex, age, presence of disease, presence of other drugs).

3. in physics, the conversion of energy from one form to another on entering a medium.