Under Section 2(1)(zg) of the Trade Marks Act, 1999, how is a "well-known trademark" defined, and what special protection does it receive under the Act?

Section 2(1)(zg) of the Trade Marks Act, 1999 defines a well-known trademark as a mark which has become so to the substantial segment of the public which uses such goods or receives such services, that its use in relation to other goods or services would be likely to indicate a connection in the course of trade between those goods/services and the owner of the well-known mark. The key protection afforded to a well-known mark is trans-class (cross-class) protection unlike ordinary registered trademarks which protect only within the specific class of goods/services for which they are registered, a well-known mark is protected across all classes. This means that a well-known mark like "TATA" or "AMUL" cannot be registered or used even for completely different categories of goods. Section 11(6)–(9) of the Act directs the Registrar to take into account the well-known status of a mark while refusing registration of a conflicting mark. The Trade Marks Registry maintains a list of well-known trademarks in India, and once declared, the mark enjoys enhanced enforcement rights even against unregistered uses.