what is a lug
noun. verb. Lug is defined as a heavy bolt used to fasten a wheel, or is slang for a big man. 1  An example of a lug is the bolt used to mount a tire.2  A man who is helpful at lifting heavy things is an example of a lug.oun. 1  A handle or projection used as a hold or support. 2  A lug nut. 3  Nautical A lugsail. 4  A projecting part of a larger piece that helps to provide traction, as on a tire or the sole of a boot.