From Longman Dictionary of Contemporary Englishbe (a figment of) somebody’s imaginationbe (a figment of) somebody’s imaginationIMAGINEto be something that someone imagines, not something that really exists or happens Did you hear that noise, or was it my imagination? These people do exist; they’re not figments of my imagination. → imagination
Examples from the Corpus
be (a figment of) somebody’s imagination• Puny appeared thoughtful, or was it his imagination?• Was it his imagination, or could he really feel the beginnings of a headache?• The real limit to whatever ingenious notions and ideas we may develop is our own imagination.• No, it was just my imagination running riot.• Yet it was not all imagination.• All that is left to connect us to the past is the imagination.• My subject was landscape and imagination.• Thoughts are things; imagination is experience. 