Two meanings:

(a) a basis for claiming injury and damages in trademark cases. Dilution refers to the idea that the commercial impact of a trademark, its connection with a particular product source, the values it is supposed to represent, or its reputation for quality will be damaged or has been damaged by the alleged infringement;

(b) a reduction in the proportion of the value of a company represented by existing shares through the issuance of new shares or rights. The latter may be addressed or prohibited by an anti-dilution clause.