The evening or day before a feast or other important celebration. Depending on local customs and practice, the celebration of a feast may begin on the eve of the feast. In many parishes, the principal Christmas services take place on Christmas Eve. The BCP provides directions for a Vigil of Pentecost (pp. 175, 227). The BOS provides forms for a Vigil for Christmas Eve, a Service for New Year's Eve (Eve of the Feast of the Holy Name), a Vigil for the Eve of All Saints' Day or the Sunday after All Saints' Day, a Service for All Hallows' Eve (Oct. 31), and a Vigil on the Eve of Baptism.
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from "An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians," Don S. Armentrout and Robert Boak Slocum, editors.