n A measure for something; a means of deriving a quantitative measurement or approximation for otherwise qualitative phenomena (especially used in Software Engineering)
n (mathematics) A measurement of the "distance" between two points in some metric space: it is a real-valued function d(x,y) between points x and y satisfying the following properties: (1) "positive definiteness": d(x,y) \ge 0 and d(x,y) = 0 \mbox{ iff } x=y , (2) "symmetric|symmetry": d(x,y) = d(y,x) , and (3) "triangle inequality": d(x,y) \le d(x,z) + d(z,y) .
v (transitive|aerospace, systems engineering) To measure or analyse statistical data concerning the quality or effectiveness of a process.