n. & v.
n. (pl. -os) 1 a the figure 0; nought. b no quantity or number; nil. 2 a point on the scale of an instrument from which a positive or negative quantity is reckoned. 3 (attrib.) having a value of zero; no, not any (zero population growth). 4 (in full zero-hour) a the hour at which a planned, esp. military, operation is timed to begin. b a crucial moment. 5 the lowest point; a nullity or nonentity.
v.tr. (-oes, -oed) 1 adjust (an instrument etc.) to zero point. 2 set the sights of (a gun) for firing. zero in on 1 take aim at. 2 focus one's attention on. zero option a disarmament proposal for the total removal of certain types of weapons on both sides. zero-rated on which no value added tax is charged. zero-sum (of a game, political situation, etc.) in which whatever is gained by one side is lost by the other so that the net change is always zero.
[ F zéro or It. zero f. OSp. f. Arab. sifr CIPHER ]