'Lag screw' definitions:

Definition of 'lag screw'

noun

A heavy woodscrew with a square or hexagonal head that is driven in with a wrench [syn: lag screw, lag bolt]

From: GCIDE

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]