flagship (n.) Look up flagship at Dictionary.com
also flag-ship, 1670s, a warship bearing the flag of an admiral, vice-admiral, or rear-admiral, from flag (n.) + ship (n.). Properly, at sea, a flag is the banner by which an admiral is distinguished from the other ships in his squadron, other banners being ensigns, pendants, standards, etc. Figurative use by 1933.