fidejussor UK /ˌfaɪdɪˈd͡ʒʌsə/US /ˌfaɪdɪˈd͡ʒʌsəɹ/ noun1 •(historical) A surety or guarantor.they also take recognizances or stipulations of certain fidejussors in the nature of bail — 1765 formsfidejussors