any disease of the mind; the psychological state of someone who has emotional or behavioral problems serious enough to require psychiatric intervention
engage or engross the interest or attention of beforehand or occupy urgently or obsessively; "His work preoccupies him"; "The matter preoccupies her completely--she cannot think of anything else"
occupy or take possession of beforehand or before another or appropriate for use in advance; "the army preoccupied the hills"
inspiring fear; "the formidable prospect of major surgery"; "a tougher and more redoubtable adversary than the heel-clicking, jackbooted fanatic"- G.H.Johnston; "something unnerving and prisonlike about high grey wall"
extremely impressive in strength or excellence; "a formidable opponent"; "the challenge was formidable"; "had a formidable array of compositions to his credit"; "the formidable army of brains at the Prime Minister's disposal"