Entry 3 senses · 2 variants Webster, 1913 Diocesan /dī-äs'-əs-ən/ · Di·oc·e·san · IPA /daɪˈɑsɪsən/ a. n. 01 a. Of or pertaining to a diocese; as, diocesan missions. 1. Of or pertaining to a diocese; as, diocesan missions. 02 n. A bishop, viewed in relation to his diocese; as, the diocesan of New York. 1. A bishop, viewed in relation to his diocese; as, the diocesan of New York. 2. The clergy or the people of a diocese.