Semitrailers are a type of trailer that is designed to be towed by a truck or tractor. They are commonly used in the transportation industry for hauling goods and materials. These trailers are also known by several other names, including tractor-trailers, semis, and 18-wheelers. Another popular synonym for semitrailers is big rigs, which refers to the large and heavy trucks that tow these trailers. Other terms used to describe these trailers include flatbeds, tankers, and refrigerated trailers. Whatever term is used, semitrailers are an essential part of the transportation industry and play a critical role in moving goods and materials across the country.