fideismPronunciation: /ˈfʌɪdɪɪz(ə)m/Definition of fideism noun [mass noun] the doctrine that knowledge depends on faith or revelation. Derivatives fideist noun fideisticPronunciation: /-ˈɪstɪk/ adjective Origin: late 19th century: from Latin fides 'faith' + -ismfideism in other Oxford dictionaries Definition of fideism in the US English dictionary