The Collaborative International Dictionary of English v.0.48:
Echo \Ech"o\ ([e^]k"[-o]), n.; pl. Echoes ([e^]k"[=o]z). [L.
echo, Gr. 'hchw` echo, sound, akin to 'hchh`, 'h^chos, sound,
noise; cf. Skr. v[=a][,c] to sound, bellow; perh. akin to E.
voice: cf. F. ['e]cho.]
1. A sound reflected from an opposing surface and repeated to
the ear of a listener; repercussion of sound; repetition
of a sound.
The babbling echo mocks the hounds. --Shak.
The woods shall answer, and the echo ring. --Pope.
2. Fig.: Sympathetic recognition; response; answer.
Fame is the echo of actions, resounding them.
Many kind, and sincere speeches found an echo in his
heart. --R. L.
(a) (Myth. & Poetic) A wood or mountain nymph, regarded as
repeating, and causing the reverberation of them.
Sweet Echo, sweetest nymph, that liv'st unseen
Within thy airy shell. --Milton.
(b) (Gr. Myth.) A nymph, the daughter of Air and Earth,
who, for love of Narcissus, pined away until nothing
was left of her but her voice.
Compelled me to awake the courteous Echo
To give me answer from her mossy couch.
4. (Whist, Contract Bridge)
(a) A signal, played in the same manner as a trump signal,
made by a player who holds four or more trumps (or as
played by some exactly three trumps) and whose partner
has led trumps or signaled for trumps.
(b) A signal showing the number held of a plain suit when
a high card in that suit is led by one's partner.
[Webster 1913 Suppl.]
Echo organ (Mus.), a set organ pipes inclosed in a box so
as to produce a soft, distant effect; -- generally
superseded by the swell.
Echo stop (Mus.), a stop upon a harpsichord contrived for
producing the soft effect of distant sound.
To applaud to the echo, to give loud and continuous
applause. --M. Arnold.
I would applaud thee to the very echo,
That should applaud again. --Shak.