|1.||informal smooth or easy progress|
|2.||nautical Compare plane sailing sailing in a body of water that is unobstructed; clear sailing|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes.|
Easy going; straightforward, unobstructed progress. For example, The first few months were difficult, but I think it's plain sailing from here on. Alluding to navigating waters free of hazards, such as rocks or other obstructions, this term was transferred to other activities in the early 1800s.