Definition of subdiaconus:
(n) :
(Anglicanism) A layperson who acts as an assistant to the deacon during the celebration of mass.
(n) :
(Eastern Orthodoxy) The highest of the minor orders below that of a deacon.
(n) :
(Catholicism, chiefly historical) A Catholic clerical rank in the major orders below that of a deacon.
(n) :
(Catholicism, chiefly historical) A Catholic cleric who assists the deacon at High Mass and normally reads the Epistle at the Eucharist.