Updated: DECEMBER 30, 2019
The term "clock" means to realize or catch on to something. It is often used when someone realizes another person is transgender, rather than cisgender. If someone guesses a person is transgender, rather than a cisgender man or woman, that person has been clocked. The term is usually applied when discussing transgender people attempting to blend in with mainstream society.
The term can be used interchangeably with the term read.
More About Clock
Transgender people may be clocked because their clothes reveal their body is not cisgender. Physical features, such as stubble or an Adam's apple on a male-to-female transgender person, can also cause someone to be clocked.
Being clocked can be humiliating and disappointing for transgender people who hope to pass as their true genders. However, this is not true for all transgender people. Some transgender people do not want to be confused with cisgender people and own their own gender presentation, even if it is atypical.
While some people do not mind being identified as trans, cisgender people should be mindful that clocking someone can offend. You may also offend someone if you presume they are trans when they are not. For this reason, it’s best to be sensitive and treat someone as they present themselves, whether you believe they are trans or not.