In terms of Passing, a Tell (noun) is a particular attribute which, when observed, significantly precludes an individual's ability to pass.
Examples of specific tells include:
- Prominent adam's apple.
- Size of hands, fingers, and feet.
- Facial hair, or lack of same.
- Height, physique, body shape.
- Obvious pattern baldness.
- Absence or presence of visible breasts.
- Facial features.