(a) the circumferential speed of a rotating wheel, bobbin, tool, etc.; (b) the speed of which a submarine is capable when moving on the surface of…

the ordinary speed of a vessel when at sea, as distinguished from full speed.

the speed of a vessel travelling stern-foremost with engines reversed.

the speed of a seaplane or hovercraft at which the drag due to the water is a maximum (cf. quots. 1914, 1935 at sense 2d).