The Collaborative International Dictionary of English v.0.48:

Desideratum \De*sid`e*ra"tum\, n.; pl. Desiderata. [L., fr.
   desideratus, p. p. See Desiderate.]
   Anything desired; that of which the lack is felt; a want
   generally felt and acknowledge. Desidiose

WordNet (r) 3.0 (2006):

desideratum
    n 1: something desired as a necessity; "the desiderata for a
         vacation are time and money"

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "desideratum":
   aim, ambition, animus, aspiration, bare necessities, call for,
   catch, counsel, dearest wish, demand, demand for, desideration,
   design, desire, determination, effect, essential, essentials,
   fixed purpose, forbidden fruit, function, glimmering goal,
   golden vision, hope, idea, indispensable, intendment, intent,
   intention, lodestone, magnet, meaning, mind, motive, must,
   must item, necessaries, necessities, necessity, need, need for,
   nisus, occasion, plan, plum, point, prerequirement, prerequisite,
   prize, project, proposal, prospectus, purpose, requirement,
   requisite, requisition, resolution, resolve, sake, striving, study,
   temptation, the necessary, the needful, trophy, view, want, will,
   wish