The Collaborative International Dictionary of English v.0.48:
Lug \Lug\ (l[u^]g), n. [Sw. lugg the forelock.]
1. The ear, or its lobe. [Scot. & Prov. Eng.]
2. That which projects like an ear, esp. that by which
anything is supported, carried, or grasped, or to which a
support is fastened; an ear; as, the lugs of a kettle; the
lugs of a founder's flask; the lug (handle) of a jug.
3. (Mach.) A projecting piece to which anything, as a rod, is
attached, or against which anything, as a wedge or key,
bears, or through which a bolt passes, etc.
4. (Harness) The leather loop or ear by which a shaft is held
5. (Zool.) The lugworm.
6. A man; sometimes implying clumsiness. [slang]
Lug bolt (Mach.), a bolt terminating in a long, flat
extension which takes the place of a head; a strap bolt.
Lug nut (Mach.), a large nut fitting a heavy bolt; -- used
especially of the nuts used to attach wheels to vehicles.
Lug wrench (Mach.), a wrench used to tighten or loosen lug
nuts, usually a steel rod having a hexagonally shaped
socket which fits closely over the lug nut; sometimes in
the shape of a cross, having several such sockets, one at
the end of each arm, to accommodate nuts of different
[1913 Webster +PJC]