On the beam; at a right angle to the centerline or keel of a vessel FM 55-501 Marine Crewman’s Handbook; being at a bearing approximately 090 Degrees or 270 Degrees relative JP 1-02 Department of Defense Dictionary of Military and Associated Terms
On the beam, that is, on a line which forms a right angle with the ship's keel; opposite to the center of the ship's side
On the beam, that is, on a line which forms a right angle with the ships keel; opposite to the center of the ships side