Definition: flagship product
A major product of a company, which is typically why the company was founded and/or what made it well known. For example, MS-DOS, Windows and the Microsoft Office suite have been flagship products of Microsoft. Photoshop is a major product of Adobe Systems, and the Mac, iPhone and iPad are flagship products of Apple.
Flagship may also refer to the most advanced product in the line. For example, a flagship smartphone is the top-end phone made by the company.
The term dates back to the 1700s where the lead ship in a naval convoy would fly a unique flag. Today, it refers to the most important product, service or location in a company.