Eas·ter 
(ēstər)
(ēstər)n.
1. A Christian feast commemorating the Resurrection of Jesus.
2. The day on which this feast is observed, the first Sunday following the full moon that occurs on or next after March 21.
3. Eastertide.
[Middle English ester, from Old English ēastre; see aus- in the Appendix of Indo-European roots.]