S: (v) preoccupy (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"
W: (adj) obsessive [Related to: obsess] (characterized by or constituting an obsession) "the obsessional character of his response"; "obsessive gambling"
W: (n) obsession [Related to: obsess] (an unhealthy and compulsive preoccupation with something or someone)