In computer graphics, a line designated by its end points (X-Y or X-Y-Z coordinates). When a circle is drawn, it is made up of many small vectors. See vector graphics
In matrix algebra, a one-row or one-column matrix.
An airplane's travel path.
The term is used generically for "pathway" or "avenue" or even an influence of some type. For example, "x, y and z provide multiple threat vectors for malware intrusion" means there are multiple ways for intrusion to occur.