(1) 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 and
graphics.
(2) In matrix algebra, a one-row or one-column matrix.
(3) An ordered list of numbers.
(4) An airplane's travel path.
(5) 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.