There are a number of synonyms that can be used for the term "double track", which generally refers to a railway line or track that consists of two parallel tracks that allow trains to run in both directions. Some common synonyms include "twin track," "dual track," and "paired track," all of which refer to a similar setup with two parallel tracks. Other possible synonyms might include "double-line track," "two-way track," or "double parallel track." Each of these terms can be used to describe a railway line with two parallel tracks, which is often used to increase the capacity and efficiency of a particular rail network.