English▸ noun
1 an enclosed space where sound reverberates:
purpose-built echo chambers allow the addition of natural-sounding reverberation to the recordings.
2 an environment in which a person encounters only beliefs or opinions that coincide with their own, so that their existing views are reinforced and alternative ideas are not considered:
people are living in partisan and ideological echo chambers
within the echo chamber of social media, it only takes a few abusive messages to start a firestorm.