lag \lag\, n.
   1. one who lags; that which comes in last. obs. "the lag of
      all the flock." --pope.
      1913 webster

   2. the fag-end; the rump; hence, the lowest class.
      1913 webster

            the common lag of people.             --shak.
      1913 webster

   3. the amount of retardation of anything, as of a valve in a
      steam engine, in opening or closing.
      1913 webster

   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.
      1913 webster

   5. zool. see graylag.
      1913 webster

   6. the failing behind or retardation of one phenomenon with
      respect to another to which it is closely related; as, the
      lag of magnetization compared with the magnetizing force
      hysteresis; the lag of the current in an alternating
      circuit behind the impressed electro-motive force which
      produced it.
      webster 1913 suppl.

   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.
      1913 webster
see also:
graylag lag of the tide priming lag screw