n.
Function: noun
Etymology: Middle English lok, from Old English loc; akin to Old High German loh enclosure and perhaps to Old English locc lock of hair
Date: before 12th century
1 a : a fastening (as for a door) operated by a key or a combination b : the mechanism for exploding the charge or cartridge of a firearm
2 a : an enclosure (as in a canal) with gates at each end used in raising or lowering boats as they pass from level to level b : AIR LOCK
3 a : a locking or fastening together b : an intricate mass of objects impeding each other (as in a traffic jam) c : a hold in wrestling secured on one part of the body broadly : a controlling hold <his paper ⋯ had a lock on a large part of the state ― John Corry>
4 : one that is assured of success or favorable outcome