lag screw

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A heavy wood screw having a square bolt head.

Century Dictionary and Cyclopedia

1. n. A flat-headed screw, used principally to attach lags to band-drums.
2. n. An iron bolt with a square or hexagonal head and cut with a wood-screw thread. It is cylindrical under the bead, so as to admit of turning after it has entered the wood. In Great Britain called coach-screw.

GNU Webster's 1913

1. n. 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.
2. n. See under Lag.

WordNet 3.0

1. n. a heavy woodscrew with a square or hexagonal head that is driven in with a wrench