1. headway(n = noun.quantity) clearance, headroom - vertical space available to allow easy passage under something;
is a kind of elbow room, room, way
2. headway(n = noun.event) head - forward movement; "the ship made little headway against the gale"
is a kind of advance, progress, progression
1. The progress made by a ship in motion; hence, progress or success of any kind. [1913 Webster]
2. Clear space under an arch, girder, and the like, sufficient to allow of easy passing underneath; clearance; headroom. [1913 Webster]
headway, n.
1 progress.
2 the rate of progress of a ship.
3 = HEADROOM 1.
N navigation, aquatics, boating, yachting, ship, oar, paddle, screw, sail, canvas, aileron, natation, swimming, fin, flipper, fish's tail, aerostation, aerostatics, aeronautics, balloonery, balloon, ballooning, aviation, airmanship, flying, flight, volitation, wing, pinion, rocketry, space travel, astronautics, orbital mechanics, orbiting, voyage, sail, cruise, passage, circumnavigation, periplus, headway, sternway, leeway, fairway, mariner, flight, trip, shuttle, run, airlift, sailing, volant, aerostatic, seafaring, nautical, maritime, naval, seagoing, coasting, afloat, navigable, aerial, aeronautic, grallatory, under way, under sail, under canvas, under steam, on the wing, in flight, in orbit, bon voyage, spread the thin oar and catch the driving gale.
N progress, progression, progressiveness, advancing, advance, advancement, ongoing, flood, tide, headway, march, rise, improvement, advancing, progressive, profluent, advanced, forward, onward, forth, on, ahead, under way, en route for, on one's way, on the way, on the road, on the high road, on the road to, in progress, in mid progress, in transitu, vestigia nulla retrorsum, westward the course of empire takes its way.