Definitions for "Counting of the Omer"
(Hebrew Sefirat ha-Omer). The counting of days between Passover and Shavuot.
The 50 days from the Feast of First Fruits to Shavuot. (See Leviticus 23:15-16)
Counting the days between Pesakh (Passover) and Shavuot (Pentecost).