Nontransmitter refers to something that does not transmit or send signals. Some synonyms for nontransmitter include inactive, passive, uncommunicative, silent, and indifferent. Inactive refers to something that is not active or engaged, while passive denotes something that is not active or actively participating. Uncommunicative means not being communicative or not expressing oneself, while silent refers to something that is not producing sound or making noise. Finally, indifferent means not showing any interest or concern. All these synonyms are useful for describing something that is not transmitting signals, and they can be used interchangeably to give a more nuanced description of the concept.