Definition of innerspring in US English:

innerspring

adjective

US
  • (of a mattress) with internal springs.

    • ‘With most inner-spring mattresses, the same gauge spring is used throughout the mattress.’
    • ‘Both inner spring mattresses and foam mattresses have their positive qualities.’

Pronunciation

innerspring

/ˈɪnərˌsprɪŋ//ˈinərˌspriNG/