The word infiltrator is typically used to describe someone or something that has entered a place or group without permission or detection. Synonyms for infiltrator include spy, mole, infiltrator, interloper, impostor, invader, intruder, trespasser, and interloper. A spy is someone who secretly gathers information, while a mole is someone who infiltrates an organization with the purpose of obtaining confidential information. An impostor is a person who pretends to be someone else in order to deceive others, while an invader is someone who enters a country or territory by force. Intruder and trespasser both suggest unlawful entry into a space. In summary, there are many synonyms for infiltrator that can be used depending on the context and intended meaning.