The Collaborative International Dictionary of English v.0.48:

Luminescent \Lu`mi*nes"cent\, a. [L. luminare to illuminate +
   -escent.] (Physics)
   Shining with a light due to any of the various causes which
   produce luminescence.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

luminescent
    adj 1: emitting light not caused by heat