Definitions
1.verb(of a sound or sound waves) To reflect off a surface and return.
2.verbTo reflect back (a sound).
3.verb(by extension) To repeat (another's speech, opinion etc.)."Sid echoed his father's point of view."
4.verbTo repeat its input as input to some other device or system.
5.verb(whist) To give the echo signal, informing one's partner about cards one holds.
6.nounThe act of something that echoes.