Buddhism - as a psychology - is the search for the Middle Path, away from the categorical and oversimplifying extremes of all or nothing judgements, out of the cognitively inflexible rut of the conditioned black and white (dichotomous) thinking.
As such, Buddhist psychology is the Psychology of Moderation.
As a psychology, Buddhism aims to restore the "flow" of the mind, by unanchoring it from what was (but no longer is) and from what will be (but isn't yet), by refocusing the mind on the present, on what still is.
As such, Buddhist psychology is the Psychology of Presence, the Psychology of Existence.
Buddhist psychology aims to help you return to a point of balance, to that proverbial center, to that dialectical pivot of "what is" - out of the categorical extremes of interpretation and judgement of others and self.
As such, Buddhist psychology is the Psychology of Compassion.
Buddhist psychology aims to de-automatize the conditioned mind - to wake up the zombie from his or her conditioned stimulus-response algorithms; to wake up the robot from his or her reflexive, conditioned, unconscious, mechanical, schematic, impulsive, compulsive automaticity; to override the default presets of our reactions with the freedom of conscious choice; i.e. to re-humanize the mind.
As such, Buddhist psychology is the Psychology of Habit Modification and Conscious Choice and Freedom. and as such, Buddhist psychology is the Psychology of Existential Rehabilitation.
Buddhist psychology doesn't just aim to wake up the brain, it tries to change it - permanently. Through consciousness-training know-how of mindfulness, the Buddhist psychology tries to override the knee-jerk limbic mind-jerks with the brakes of frontal lobe activity.
As such, Buddhist psychology is the Psychology of Neural Plasticity.
Buddhist psychology aims to increase mindfulness to facilitate change of what can be changed and to facilitate the wisdom of letting what cannot be changed just be as it is.
As such, Buddhist psychology is the Psychology of Acceptance, of Dialectical Wisdom, not of passivity.
But, in the final analysis, "Buddhist Psychology" is just a phrase...