The term "trucking rig" can refer to a wide variety of large vehicles used for transportation. Here are some synonyms that can be used instead of "trucking rig": 1. Big rig - This term is commonly used in the United States to refer to a large commercial truck. 2. 18-wheeler - This term primarily describes trucks that have 18 wheels and are used to haul heavy loads. 3. Semi-truck - A semi-truck is a type of truck that has a tractor unit and a semi-trailer to transport goods. 4. Trailer truck - This term describes trucks typically used for long-haul deliveries that have a separate trailer attachment. 5. Haulage truck - This term is primarily used in the UK and other Commonwealth countries to describe large lorries used to transport goods.