In astrology, an intercepted sign is one that is completely within an astrological house and does not appear on the cusp of that house. These always appear in pairs, with another sign also intercepted on the opposite side of the zodiac. For example, if Aries is intercepted in the second house, Libra will be intercepted in the eighth house.
The imagery of a sign being hidden within a house gives rise to the interpretation that intercepted signs relate to the unconscious mind. So, it is quite likely that if there are many planets in an intercepted sign, the person can have a powerful unconscious related to those planets. However, since it is within a house, the implication is that it may be challenging to access those unconscious strengths.