Source : Webster's Revised Unabridged Dictionary (1913)

Lag \Lag\, n.
   1. One who lags; that which comes in last. [Obs.] ``The lag
      of all the flock.'' --Pope.

   2. The fag-end; the rump; hence, the lowest class.

            The common lag of people.             --Shak.

   3. The amount of retardation of anything, as of a valve in a
      steam engine, in opening or closing.

   4. A stave of a cask, drum, etc.; especially (Mach.), one of
      the narrow boards or staves forming the covering of a
      cylindrical object, as a boiler, or the cylinder of a
      carding machine or a steam engine.

   5. (Zo["o]l.) See {Graylag}.

   {Lag of the tide}, the interval by which the time of high
      water falls behind the mean time, in the first and third
      quarters of the moon; -- opposed to {priming} of the tide,
      or the acceleration of the time of high water, in the
      second and fourth quarters; depending on the relative
      positions of the sun and moon.

   {Lag screw}, an iron bolt with a square head, a sharp-edged
      thread, and a sharp point, adapted for screwing into wood;
      a screw for fastening lags.