A Royal Navy midshipman ranks immediately below a Second Lieutenant in the Army or Pilot Officer RAF. His rank insignia is a white patch with a buttonhole and gold button on the collar.
In the United States Navy a midshipman is for all intents and purposes of an officer cadet. His rank insignia is a plain gold anchor worn on the collar.
The word midshipman derives from the part of ship, amidships, which was their station.