Pentecost

Boyd’s Bible Dictionary:

(fiftieth day). The Hebrew harvest-home festival, celebrated on fiftieth day from the Passover, or on the date of the giving of the law at Sinai (Ex. 23:16; 34:22; Lev. 23:15-22; Num. 28). Christ died on the day of the Passover. Fifty days later, after His resurrection and ascension to glory, on the day of Pentecost, the Church was formed by the descent and indwelling of believers by the Holy Spirit (Acts 2:1-14).

Concise Bible Dictionary:

This name which signifies “fiftieth” is found only in the New Testament: it corresponds to the FEAST OF WEEKS. From the waving of the sheaf of firstfruits fifty days were counted, and on the day after the seven sabbaths the feast was kept. A new meat offering of two loaves baken with leaven was offered; also seven lambs, one bullock, and two rams for a burnt offering, with their meat and drink offerings “even an offering made by fire of sweet savor unto the Lord.” Also one kid of the goats for a sin offering; and two lambs for a peace offering. It was proclaimed a holy convocation, in which no servile work was to be done (Lev. 23:15-21). The Israelites came with their free-will offerings unto Jehovah, according as He had blessed them. See OFFERINGS.
The feast is typical of the presentation of the saints in the power and sanctification of the Holy Spirit. It was to be a day of universal rejoicing before the Lord (Deut. 16:9-12), and was the commencement of the ingathering of the harvest. It is not mentioned in Ezekiel’s future feasts, because it has been fulfilled in the present interval in God’s dealings with Israel (compare John 7:37-39). See FEASTS.

Strong’s Dictionary of Greek Words:

Greek:
πεντηκοστή
Transliteration:
pentekoste
Phonic:
pen-tay-kos-tay’
Meaning:
feminine of the ordinal of 4004; fiftieth (2250 being implied) from Passover, i.e. the festival of "Pentecost"
KJV Usage:
Pentecost

Jackson’s Dictionary of Scripture Proper Names:

fiftieth

Potts’ Bible Proper Names:

Fiftieth:―festival celebrated on fiftieth day from Passover, Acts 2:1. {Quinquagesimus}