The most formal name for Easter is 'Ülestõusmispüha' the term literally translates as 'Resurrection holiday'. Then there is the less formal 'Lihavõtted' that means 'meat taking' referring to the end of lent when you can eat meat again. My preferred way to say Easter is 'Munadepühasid' as it relates to eggs and means 'egg holiday'. There are several ways you can wish someone a happy Easter using this term - 'Häid Munadepühasid', Ilusaid Munadepühasid or Rõõmsaid Munadepühasid.
So however you wish to say it, I wish you all a happy, joyful and beautiful Easter!