The phrase "pinned down" refers to being stuck or trapped in a particular situation. Synonyms for this phrase include "cornered," "constrained," "enclosed," "immobilized," "confined," "restricted," "trapped," and "stuck." Each of these words describes a feeling of being unable to move or act freely. For example, one might feel "cornered" in a difficult conversation, or "confined" by the rules of a restrictive job. Regardless of the synonym used, the sense of being "pinned down" suggests a feeling of limitation or restriction that can be frustrating or uncomfortable.