That depends on the context. One typical meaning is "Connections are made in the field", as in, cables that aren't provided with connectors attached. The connectors are then terminated in the field.
Another meaning can be just any connection that is wired to a device on installation, such as motor leads.
From the standpoint of typical integrators, who build electrical panels, with starters, drives, plc's, relays, etc., any wire that has to be connected 'off the panel' is a field termination.