Bending outward. A convex lens or mirror has at least one side that bulges outward. A convex lens produces converging light rays. A convex mirror produces diverging rays. See also reflect, refract, focal length, focal point
A convex polygon or polyhedron contains no holes or indentions. If one constructs a line segment between any two points of a convex object, then every point on the line segment is part of the object. The pentagram is a non-convex polygon; the Kepler-Poinsot solids are non-convex polyhedra.
Said of a new camshaft lifter. The lifter bottom is rounded with the lowest point occurring near the center, so it will contact the camshaft lobe somewhere near its center, rather than wearing the edges.
When an 2D/3D-object is convex, you can draw a straight line through it, and it enters the 2D/3D-object only one time on its route through, and leaves it only one time. The opposite of convex is converge.