Final answer:
The term that describes an actor positioning themselves so as not to be seen by the audience is 'masked'. This is a stagecraft technique allowing actors to remain unseen for dramatic effect or to enable smooth scene transitions.
Step-by-step explanation:
When an actor comprises his or her body position so that the audience can't see him or her, he or she is said to be masked. The term refers to the practice in theater where an actor strategically positions themselves on stage so that they are out of view of the audience, often behind a set piece or another actor, in a way that blends with the environment or is out of the direct line of sight.
Use of body positioning is a fundamental aspect of stagecraft that allows for smooth transitions and unseen movement during a performance. While terms like obscured, hidden, and camouflaged can also describe an actor who is not visible to the audience, the specific scenario described, where an actor adjusts their body position to avoid being seen, is most directly referred to as being masked.