Crossrail is a term used to describe a specific railway project in the United Kingdom. However, there are several synonyms that can be used to describe similar train networks and transportation routes. Some synonymous phrases for crossrail might include "underground railway," "commuter rail," "light rail," or "mass transit." These terms all describe forms of transportation that move people around urban areas in a convenient and efficient manner. Depending on the specific region or country, there may be other phrases that are used to describe similar rail networks. However, all of these transportation systems aim to streamline travel and reduce congestion on the roads.