[sub.tend] vt [L subtendere to stretch beneath, fr. sub- + tendere to stretch--more at thin] (1570) 1 a: to be opposite to and extend from one side to the other of "a hypotenuse ~s a right angle" b: to fix the angular extent of with respect to a fixed point or object taken as the vertex "the angle ~ed at the eye by an object of given width and a fixed distance away" "a central angle ~ed by an arc" c: to determine the measure of by marking off the endpoints of "a chord ~s an arc"
2. a: to underlie so as to include b: to occupy an adjacent and usu. lower position to and often so as to embrace or enclose "a bract that ~s a flower"