To proceed or develop with comparative slowness: The electric current lags behind the voltage.
To fail, weaken, or slacken gradually; flag.
Games To determine the order of play in billiards by successively hitting the cue ball against the end rail, the ball rebounding closest to the head rail indicating the player to shoot first.
v.
tr.
To cause to hang back or fall behind.
To shoot, throw, or pitch (a coin, for example) at a mark.
n.
The act, process, or condition of lagging.
One that lags.
A condition of slowness or retardation.
The extent or duration of lagging: "He wondered darkly at how great a lag there was between his thinking and his actions"(Thomas Wolfe).
An interval between events or phenomena considered together.
[From earlier lag, last person, from Middle English lag-, last (in lagmon, last man), perhaps of Scandinavian origin.] lag'ger n.
[lag-er] 
ər