See anyone in the mouth gag - silence is not a good your side.
From a spiritual perspective a gag is anything that stops us from communicating effectively. This will encompass both negative and positive aspects; that is, when prudence dictates that we say nothing or when an external condition forcibly restrains us. Many people have difficulty in expressing their emotions, so a gag in dreams may symbolize the underlying emotional difficulty that prevents us from doing so. This might, for instance, be childhood trauma or the feeling that we will not be listened to. To gag, as in experiencing nausea, suggests we are trying to get rid of negative feelings. If we are being gagged in a dream then there is a strong possibility that in waking life we are being prevented from expressing an opinion over something we feel to be important. If we are doing the gagging then we will be suppressing our ability to speak clearly or honestly. You might also like to consult the entries for Talking and Vomit.