1. To locate someone or something using one's sense of smell. Almost exclusively said of dogs or other animals. A noun or pronoun can be used between "smell" and "out." The police use specially trained dogs to smell out criminals. After receiving a bomb threat at the stadium, search dogs were brought in to smell it out.

2. By extension, to uncover, reveal, or expose someone or something through some form of investigation. A noun or pronoun can be used between "smell" and "out." If the company is up to anything fishy, the auditor will smell it out. Our lead investigative journalist smelled out some major corruption between the senator and foreign investors.