The most solemn Christian festival, which celebrates the resurrection of Jesus Christ. It is a movable feast: its date each year is determined by the phases of the moon, i.e. the first Sunday after the first full moon of the vernal equinox. There had been controversy about its determination, dividing the Celtic (i.e. Irish) and Roman churches, but this was settled for England at the *Synod of *Whitby in 664. [< OldEngl. Eostre = goddess of spring] -
Cf. Tonsure
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.