Pilot watches were ones that were specifically issued to pilots during WWII most notably those in the German Air force “Luftwaffe”. These watches were made to be easy to read at a glance and accurate. They were also meant to be worn over the pilots jacket and thus ended up with a diameter of over 50mm and a simple dial design, that could be easily read at a glance. And a large crown that could be operated while wearing gloves. There were some variations of this theme, like watches specifically designed for the navigators,and many countries issued watches to their pilots. Back in those days it really was a useful tool and not just a cool accessory to have, their survival depended on the accuracy and reliability of their analog instruments to aid in their navigation and to keep track of certain things like speed and fuel, the watches ended up as a sort of Back up. These guys were the real deal, going up against their rival combatants and their survival or victories depended mostly on their skills and sheer brazenness “(Balls in today’s language)”.
Today Pilot watch seems more like a design style than an actual specialized tool critical for pilots. Some common features are sharply angled hands, Slide Rule, simple to read dial, or on the opposite end a crowded dial with lots of tinny numbers and such things that would theoretically be useful to a pilot today. ie… the Hamilton X-wind which has two independently operated bezels (with very small numbers) which can be used to calculate a crosswind. But I cant imagine a pilot coming down for a landing, lining up with the runway and then, droping everything and start fiddling with his watch at the last minute. GMT function has also been incorporated into pilot watches and helps keep track of a second time zone.