[1] : The Collaborative International Dictionary of English v.0.48

tautological \tau`tolog"ical\, a. cf. f. tautologique.
   involving tautology; having the same signification; as,
   tautological expression. -- tau`tolog"ically, adv.
   1913 webster

   tautological echo, an echo that repeats the same sound or
      syllable many times.
      1913 webster
see also:
tau`tolog"ically tautological echo 

Echo >> E Words
Echo, definition of term: Echo
echo_pag1.html

Tautological >> T Words
Tautological, definition of term: Tautological
tautological_pag1.html

Echo Sounding >> E Words
Echo Sounding, definition of term: Echo Sounding
echo+sounding_pag1.html