The definition of collinear is in or sharing the same straight line.
An example of collinear used as an adjective is in the phrase "collinear points," which means points that are on the same line.
in, or sharing, the same straight line, as two points or planes
Origin of collinearcol- (var. of com-) + linear
- Passing through or lying on the same straight line.
- Containing a common line; coaxial.
- lying on the same straight line