n. The act or state of adhering, or of being united and attached; close connection or association: as, the adhesion of parts united by growth, cement, etc.; inflammatory adhesion of surfaces in disease.n. Steady attachment of the mind or feelings; firmness in opinion; adherence: as, an adhesion to vice.n. Assent; concurrence.n. That which adheres; accretion.n. In physical, molecular attraction exerted between the surfaces of bodies in contact, as between two solids, a solid and a liquid, or a solid and a gas. See extract, and cohesion.n. In botany, the union of parts normally separate. In pathology, especially in the plural, the adventitious bands or fibers by which inflamed parts have adhered, or are held together. In surgery, the reunion of divided parts by a particular kind of inflammation, called the adhesive. In mech., often used as synonymous with friction (which see).n. An expression of, or the act by which one expresses, acquiescence in, adherence to, and support of some statement, declaration, or proposal; assent; concurrence.