[ 'pɛntɪkɒst ]
■ noun
1》 the Christian festival celebrating the descent of the Holy Spirit on the disciples of Jesus after his Ascension, held on Whit Sunday.
2》 the Jewish festival of Shavuoth.
Origin
OE pentecosten , via eccles. L. from Gk pentēkostē (hēmera) 'fiftieth (day)' (because the Jewish festival is held on the fiftieth day after the second day of Passover).