Trucker's Rig is a term used to describe the combination of a tractor and trailer used by truckers. The term 'SEMI' is often used to refer to this combination, as it is a shortened version of the word 'SEMI-trailer'. A SEMI-trailer is a trailer that is connected to the tractor with a fifth wheel coupling, allowing the trailer to pivot and turn with the tractor. This type of trucking rig is commonly used for long-distance hauling of goods.