Noun
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
Source: WordNetAs a sidelight, the issue came up after a merchant questioned a city utility employee about wasting gas by parking a city pickup with the motor running while doing work. Source: Internet
But competition is a sidelight for him, a distraction from his real passion: tying on his Brooks running shoes and getting in the road alone, day after day, week after week. Source: Internet