ECHOMETER
E*chom"e*ter, n. Etym: [Gr. -meter: cf. F. échomètre.] (Mus)

Defn: A graduated scale for measuring the duration of sounds, and determining their different, and the relation of their intervals. J. J. Rousseau.

ECHOMETRY
E*chom"e*try, n. Etym: [Cf. F. échométrie.]

1. The art of measuring the duration of sounds or echoes.

2. The art of constructing vaults to produce echoes.

ECHON; ECHOON
Ech*on", Ech*oon", pron.

Defn: Each one. [Obs.] Chaucer.

ECHOPATHY
E*chop"a*thy, n. [Echo + -pathy, as in homeopathy.] (Med.)

Defn: A morbid condition characterized by automatic and purposeless repetition of words or imitation of actions.

ECHOSCOPE
Ech"o*scope, n. Etym: [Gr. -scope.] (Med.)