To dream of a polygraph test represents social verification of intentions. Having to show someone with your actions that you are being honest beyond any doubt. A reflection of a loss of confidence or faith.
Alternatively, it may reflect a need to prove that you or someone else doesn’t really care about something. Honesty, fear, or, jealousy being put to the test.
Example: A man dreamed of having to take a polygraph test. In waking life his girlfriend forced him to embarrass another woman to prove to her that he didn’t like the other woman.