Force implies strength greater than our own, in this context spiritual strength and awareness. Psychic disturbance and spiritual presence is often felt by many sensitives as an inexorable force.
Psychological / emotional perspective: Often in dreams we become aware of energies and forces that seem to be beyond our control. These may often be potentials that we can understand and manage with greater understanding.
Material aspects: Pressure and stress in day-to-day living may show itself in dreams as a force that needs to be controlled.