a person who passes time in a lazy or unproductive way.

Machinery . an idle gear, wheel, or pulley.

Railroads . an empty freight car placed under the projecting end of a long object carried by the next car, so that the latter can be connected with another part of the train.

Nautical . day man ( def. 2 ) .

noun

slacker , drone , couch potato * , loafer , lazy bum , bum , fainant , good-for-nothing , layabout , ne\'er-do-well , no-good , slugabed , sluggard , dawdler , do-nothing , donothing , faineant , lazybones , loiterer , lounger , tramp , trifler