sidelight sidelight /ˈsaɪdlaɪt/

noun

1. Light carried by a boat that indicates the boat's direction; vessels at night carry a red light on the port bow and a green light on the starboard bow  ( running light , sidelight )
   light carried by a boat that indicates the boat's direction; vessels at night carry a red light on the port bow and a green light on the starboard bow