Having value that is not acknowledged.

synoniemen: unappreciated, unsung.

Roget 483: depreciating, depreciated etc. v.; unvalued, unprized^†.   

Roget 866: indifferent, cold, frigid, lukewarm; cool, cool as a cucumber; unconcerned, insouciant, phlegmatic, pococurante^†, easygoing, devil-may-care, careless, listless, lackadaisical; half-hearted; unambitious, unaspiring, undesirous^†, unsolicitous^†, unattracted.    [indifferent toward people] aloof, unapproachable, remote; uncaring.    unattractive, unalluring, undesired, undesirable, uncared for, unwished^†, unvalued, all one to.    insipid etc. 391; vain.    ... meer laten zien