React and Echo

react

Show a response or a reaction to something.
- synonyms: respond
Act against or in opposition to.
- usage: "She reacts negatively to everything I say"
- synonyms: oppose
Undergo a chemical reaction; react with another substance under certain conditions.
- usage: "The hydrogen and the oxygen react"

(v.t.) To act or perform a second time; to do over again; as, to react a play; the same scenes were reacted at Rome.
(v.i.) To act upon each other; to exercise a reciprocal or a reverse effect, as two or more chemical agents; to act in opposition.
(v.i.) To return an impulse or impression; to resist the action of another body by an opposite force; as, every body reacts on the body that impels it from its natural state.

Webster's Revised Unabridged Dictionary

(Military) REACT stands for rapid execution and combat targeting

Department of Defense Dictionary of Military and Associated Terms. 31 January 2011.

echo

The repetition of a sound resulting from reflection of the sound waves.
- usage: "she could hear echoes of her own footsteps"
- synonyms: reverberation, sound reflection, replication
Greek mythology. ( a nymph who was spurned by Narcissus and pined away until only her voice remained)
A reply that repeats what has just been said.
A reflected television or radio or radar beam.
A close parallel of a feeling, idea, style, etc..
- usage: "his contention contains more than an echo of Rousseau"; "Napoleon III was an echo of the mighty Emperor but an infinitely better man"
An imitation or repetition.
- usage: "the flower arrangement was created as an echo of a client's still life"

To say again or imitate.
- usage: "followers echoing the cries of their leaders"
- synonyms: repeat
Ring or echo with sound.
- usage: "the hall resounded with laughter"
- synonyms: resound, ring, reverberate
Call to mind.
- usage: "His words echoed John F. Kennedy"
- synonyms: recall

(v.t.) To repeat with assent; to respond; to adopt.
(n.) Fig.: Sympathetic recognition; response; answer.
(n.) A nymph, the daughter of Air and Earth, who, for love of Narcissus, pined away until nothing was left of her but her voice.
(v.i.) To give an echo; to resound; to be sounded back; as, the hall echoed with acclamations.
(n.) A wood or mountain nymph, regarded as repeating, and causing the reverberation of them.
(v.t.) To send back (a sound); to repeat in sound; to reverberate.
(n.) A sound reflected from an opposing surface and repeated to the ear of a listener; repercussion of sound; repetition of a sound.
(n.) 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.
(n.) A signal showing the number held of a plain suit when a high card in that suit is led by one's partner.

Webster's Revised Unabridged Dictionary

Echo is either masculine or feminine given name

(Military) ECHO stands for European Community Humanitarian Aid Department

Department of Defense Dictionary of Military and Associated Terms. 31 January 2011.