a ship carrying the flag officer or the commander of a fleet, squadron, or the like, and displaying the officer's flag.

the main vessel of a shipping line.

any of the best or largest ships or airplanes operated by a passenger line.

the best or most important one of a group or system

This store is the flagship of our retail chain.

being or constituting a flagship.

noun

bellwether , chief , crown jewel , flotilla leader , forerunner , front runner , head , lead ship , mother ship