Any of a group of early Christians who celebrated Easter on the day of the Jewish Passover (the 14th of Nisan), whether this was a Sunday or not.
The practice (chiefly observed in Proconsular Asia) was condemned by the Council of Nicaea, a.d. 325.
Of or relating to the Quartodecimans, or their method of observing Easter.
Late Middle English; earliest use found in John Trevisa (c1342–?1402), translator. From post-classical Latin quartadecimanus, quartodecimanus member of a group of early Christians who celebrated Easter on the 14th day from classical Latin quartus decimus fourteenth (from quartus fourth + decimus tenth) + -ānus.