What is Fighter Brand?

Legal Definition
In marketing, a fighter brand (sometimes called a fighting brand) is a lower-priced offering launched by a company to take on, and ideally take out, specific competitors that are attempting to under-price them. Unlike traditional brands that are designed with target consumers in mind, fighter brands are created specifically to combat a competitor that is threatening to take market share away from a company's main brand.

A related concept is the flanker brand, a term often found in the mobile phone industry. In the case of flankers, or multibranding, the products may be identical to the main offerings and the new brand is used to expand product placement.
-- Wikipedia