The semisquare aspect in astrology is where two planets are 45° degrees apart and indicate blocked energy. This is related to the square aspect but it is only half the angle. This is where the circle is divided by eight.
Square aspects tend to indicate energy that is blocked between two planets or parts of the individuals psyche. With the semisquare aspect, this energy appears to be even more deeply blocked and thus it manifests as external events. A person is forced to address difficulties in their psyche because these continually manifest as events in the outside world that need dealing with. With this fact, semisquares can lead a person to great achievements as the energy of the square aspect is given tangible form in the external world.
People with these aspects, often develop great persistance, endurance and productive results in their efforts to control and reconcile these difficult combinations of energy.