Z

[zero hour]{n.} 1. The exact time when an attack or other military action is supposed to start. •/Zero hour for the bombers to take off was midnight./ 2. The time when an important decision or change is supposed to come; the time for a dangerous action. •/It was zero hour and the doctor began the operation on the man./ •/On the day of the championship game, as the zero hour came near, the players grew nervous./

[zero in on]{v.} 1. To adjust a gun so that it will exactly hit (a target); aim at. •/Big guns were zeroed in on the enemy fort./ •/American missiles have been zeroed in on certain targets, to be fired if necessary./ 2. {slang} To give your full attention to. •/The Senate zeroed in on the Latin-American problems./ •/Let’s zero in on grammar tonight./

[zip one’s lip] See: BUTTON ONE’S LIP.

[zone defense]{n.} A defense in a sport (as basketball or football) in which each player has to defend a certain area. •/The coach taught his team a zone defense because he thought his players weren’t fast enough to defend against individual opponents./

[zonk out]{v. phr.}, {slang} 1. To fall asleep very quickly. •/Can I talk to Joe??—?Call back tomorrow, he zonked out./ 2. To pass out from fatigue, or alcohol. •/You won’t get a coherent word out of Joe, he has zonked out./

[zoom in]{v. phr.} 1. To rapidly close in on (said of airplanes and birds of prey). •/The fighter planes zoomed in on the enemy target./ 2. To make a closeup of someone or something with a camera. •/The photographer zoomed in on the tiny colibri as it hovered over a lovely tropical flower./