desideratum

necessary, needful (requisite)., fated; destined; elect; spellbound., compulsory (compel); uncontrollable, inevitable, unavoidable, irresistible, irrevocable, inexorable; avoidless, resistless., involuntary, instinctive, automatic, blind, mechanical; unconscious, unwitting, unthinking; unintentional (undesigned); impulsive.