the outer boundary of an artifact or a material layer constituting or resembling such a boundary | any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. |
a device that provides reactive force when in motion relative to the surrounding air; can lift or control a plane in flight | a mixture containing two or more metallic elements or metallic and nonmetallic elements usually fused together or dissolving into each other when molten |
a superficial aspect as opposed to the real nature of something | |
information that has become public | |
the extended two-dimensional outer boundary of a three-dimensional object | |
the outermost level of the land or sea | |