1 [count] : a device that keeps something (such as a door, window, or box) from being opened and that is usually opened by using a key
▪ We had no key so we had to break the lock to open the door. ▪ The thief used a wire to pick the lock. — see also combination lock, padlock 2 [count] : an area in a canal or river that has gates at each end which are opened and closed to control the level of the water in different sections of the canal or river as boats move through it 3 [count] : a method of holding someone so that the person being held cannot move
▪ a leg lock — see also headlock 4 US, informal a [singular] : complete control of something
▪ He appears to have a lock on the nomination for governor. [=he appears to be sure of getting the nomination for governor] ▪ He has been able to get a lock on the nomination. ▪ There seems to be no danger that the company will lose its lock on the industry.
b [count] : someone or something that is certain to have or do something — usually singular ▪ He's a lock for the nomination. = He's a lock to get the nomination. [=he is certain to get the nomination] ▪ The team is a lock to win the championship.
c [count] : something that is certain to happen — usually singular ▪ It looks like his nomination is a lock. 5 [count, noncount] Brit : the extent to which the front wheels of a vehicle can be turned
▪ a car on full lock [=a car with its wheels turned as far as possible]