Real Dictionary

gridlock
uncountable noun: Gridlock is the situation that exists when all the roads in a particular place are so full of vehicles that none of them can move.
uncountable noun: You can use gridlock to refer to a situation in an argument or dispute when neither side is prepared to give in, so no agreement can be reached.

gridlock in American English
a traffic jam, as at an intersection, in which no vehicle can move in any direction
noun: the stoppage of free vehicular movement in an urban area because key intersections are blocked by traffic

gridlock in British English
noun: obstruction of urban traffic caused by queues of vehicles forming across junctions and causing further queues to form in the intersecting streets
verb: (of traffic) to block or obstruct (an area)