1. 旗舰;(尤指指挥官所在的)主舰
A flagship is the most important ship in a fleet of ships, especially the one on which the commander of the fleet is sailing.

2. 王牌;主打产品;旗舰产品
The flagship of a group of things that are owned or produced by a particular organization is the most important one.

1. the ship that carries the commander of a fleet and flies his flag

2. the chief one of a related group

e.g. it is their flagship newspaper