Source : Webster's Revised Unabridged Dictionary (1913)

Lagging \Lag"ging\, n.
   1. (Mach.) The clothing (esp., an outer, wooden covering), as
      of a steam cylinder, applied to prevent the radiation of
      heat; a covering of lags; -- called also {deading} and
      {cleading}.

   2. Lags, collectively; narrow planks extending from one rib
      to another in the centering of arches.

Lag \Lag\, v. i. [imp. & p. p. {Lagged}; p. pr. & vb. n.
   {Lagging}.]
   To walk or more slowly; to stay or fall behind; to linger or
   loiter. ``I shall not lag behind.'' --Milton.

   Syn: To loiter; linger; saunter; delay; be tardy.

Source : WordNet®

lagging
     n : used to wrap around pipes or boilers or laid in attics to
         prevent loss of heat

lag
     n 1: the act of slowing down or falling behind [syn: {slowdown},
          {retardation}]
     2: the time between one event, process, or period and another
        [syn: {interim}]
     3: one of several thin slats of wood forming the sides of a
        barrel or bucket [syn: {stave}]
     [also: {lagging}, {lagged}]

lag
     v 1: hang (back) or fall (behind) in movement, progress,
          development, etc. [syn: {dawdle}, {fall back}, {fall
          behind}]
     2: lock up or confine, in or as in a jail; "The suspects were
        imprisoned without trial"; "the murderer was incarcerated
        for the rest of his life" [syn: {imprison}, {incarcerate},
         {immure}, {put behind bars}, {jail}, {jug}, {gaol}, {put
        away}, {remand}]
     3: throw or pitch at a mark, as with coins
     4: cover with lagging to prevent heat loss; "lag pipes"
     [also: {lagging}, {lagged}]

lagging
     See {lag}