The Collaborative International Dictionary of English v.0.48:

Echo \Ech"o\, v. t. [imp. & p. p. Echoed; p. pr. & vb. n.
   Echoing. -- 3d pers. sing. pres. Echoes.]
   1. To send back (a sound); to repeat in sound; to
      reverberate.
      [1913 Webster]

            Those peals are echoed by the Trojan throng.
                                                  --Dryden.
      [1913 Webster]

            The wondrous sound
            Is echoed on forever.                 --Keble.
      [1913 Webster]

   2. To repeat with assent; to respond; to adopt.
      [1913 Webster]

            They would have echoed the praises of the men whom
            they envied, and then have sent to the newspaper
            anonymous libels upon them.           --Macaulay.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

echoing \echoing\ adj.
   Reflecting sounds so as to create multiple echoes; as, a
   hotel with echoing halls.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

echoing
    adj 1: (of sounds) repeating by reflection; "a hotel with
           echoing halls" [syn: echoing(a), reechoing]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "echoing":
   answering, antiphonal, battological, booming, confutative,
   duplicative, echoic, growling, imitative, iterative, lingering,
   parrotlike, persistent, reboant, rebounding, recapitulative,
   redundant, reduplicative, reechoing, refutative, reiterant,
   reiterative, rejoining, repeating, repercussive, repetitional,
   repetitionary, repetitious, repetitive, replying, resounding,
   respondent, responding, responsive, returning, reverberant,
   reverberating, reverberatory, rumbling, sounding, tautological,
   tautologous, thundering, undamped