1. insulation used to prevent heat diffusion, as from a steam pipe.
2. A wooden frame built especially to support the sides of an arch until the keystone is positioned.

1. falling behind, not keeping up the pace
2. occurring after; indicating the later phase of
3. the covering of something with strips of felt, wood etc, either as insulation or for protection
4. the material so used
5. present participle of lag.

1. 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.

1. the act of walking or moving slowly, or of falling behind.
2. in architecture, the planking, consisting of narrow strips, extending from one rib of the centering of an arch, vault, or tunnel to another, and affording direct support to the voussoirs until the arch or vault is closed in.
3. in mining, strips of wood or light timbers laid across the stulls in the drifts to prevent fragments of rock from falling through.
4. in machinery, same as deading.
5. A covering for the face of a pulley, designed to increase its effective diameter or to augment the adhesion of the belt.
6. same as lag, n., 7.
7. nautical, the part of a barrel-stave beyond the head. also spelled laggin.

1. used to wrap around pipes or boilers or laid in attics to prevent loss of heat