What is "lag of the tide"

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.

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.

   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.