To dream that you are in your underwear represents a condition that has formed a loss of reverence for yourself. On the other hand, it may even represent some facet of your private life. If you feel guilty about being seen in your underwear, then the dream indicates that you have some hesitance about revealing your true viewpoints, hidden ideas/behavior, and thoughts.
To dream that someone other than you is in their underwear represents a curious and awkward situation. You may even see that person for who they really are.
To see tattered or sullied underwear represents that you aren't comfortable with yourself and may have some feelings of failure. You may even have critical and negative feelings about yourself. You may feel uneasy regarding your sexuality