The term "most trafficable" refers to the ease with which traffic can pass through a particular area or object. The opposite of this term can be described as "least trafficable," which refers to an area or object that is difficult or impossible to navigate through. A road that is rocky or covered in debris may be considered least trafficable, while a smooth, well-paved road would be most trafficable. Similarly, a congested, narrow street may be least trafficable, while a wide, spacious boulevard would be most trafficable. In summary, antonyms for the term "most trafficable" could include difficult, inaccessible, challenging, obstructed, or impassable.