the outer boundary of an artifact or a material layer constituting or resembling such a boundary | a step in walking or running |
a device that provides reactive force when in motion relative to the surrounding air; can lift or control a plane in flight | structural member consisting of the horizontal part of a stair or step |
a superficial aspect as opposed to the real nature of something | the part (as of a wheel or shoe) that makes contact with the ground |
information that has become public | the grooved surface of a pneumatic tire |
the extended two-dimensional outer boundary of a three-dimensional object | |
the outermost level of the land or sea | |