Progress or advancement that is free from hassle and easy to achieve. If we can just get the application approved, it should be smooth sailing from there. Organizing the event was really stressful, but it was pretty smooth sailing on the day.
Easy progress, as in We had a hard time setting up the new computer system but it'll be smooth sailing from here on . The smooth in this idiom alludes to calm waters, free from big waves or roughness, a usage dating from the late 1300s. The transfer to other kinds of easy progress dates from the second half of the 1900s. Also see plain sailing.
Perfectly straightforward; an easy and unobstructed course. The term comes from navigation, where it means sailing in waters that are free of hazards, particularly rocks or other obstructions. Used since the nineteenth century, it may have come from the earlier navigational term plane sailing, the art of determining a ship’s position without reference to the fact that the earth is round, and therefore sailing on a plane (flat surface), which works, but only for a short distance. Plain sailing was transferred to other pursuits in the early nineteenth century. Shaw used it in his preface to Androcles and the Lion (1916): “Without the proper clues the gospels are . . . incredible. . . . But with the clues they are fairly plain sailing.” A synonymous term is smooth sailing, used figuratively since the first half of the 1800s. Edward Bulwer Lytton had it in Night and Morning (1841), “‘Oh, then it’s all smooth sailing,’ replied the other.” See also hard/tough sledding.