The Collaborative International Dictionary of English v.0.48:

Reverential \Rev`er*en"tial\, a. [Cf. F. r['e]v['e]renciel. See
   Reverence.]
   Proceeding from, or expressing, reverence; having a reverent
   quality; reverent; as, reverential fear or awe. "A
   reverential esteem of things sacred." --South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

reverential
    adj 1: feeling or manifesting veneration [syn: respectful,
           reverential, venerating]