Concise Bible Dictionary:

The name given to any from among the nations who embraced Judaism (Acts 2:1010Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes, (Acts 2:10); Acts 6:55And the saying pleased the whole multitude: and they chose Stephen, a man full of faith and of the Holy Ghost, and Philip, and Prochorus, and Nicanor, and Timon, and Parmenas, and Nicolas a proselyte of Antioch: (Acts 6:5); Acts 13:4343Now when the congregation was broken up, many of the Jews and religious proselytes followed Paul and Barnabas: who, speaking to them, persuaded them to continue in the grace of God. (Acts 13:43)). The name may be said to be a Greek word, derived from “to come to.” It is used by the LXX where the Hebrew has “the stranger” that sojourneth among you (Ex. 12:48-4948And when a stranger shall sojourn with thee, and will keep the passover to the Lord, let all his males be circumcised, and then let him come near and keep it; and he shall be as one that is born in the land: for no uncircumcised person shall eat thereof. 49One law shall be to him that is homeborn, and unto the stranger that sojourneth among you. (Exodus 12:48‑49); Lev. 17:8,10,12-158And thou shalt say unto them, Whatsoever man there be of the house of Israel, or of the strangers which sojourn among you, that offereth a burnt offering or sacrifice, (Leviticus 17:8)
10And whatsoever man there be of the house of Israel, or of the strangers that sojourn among you, that eateth any manner of blood; I will even set my face against that soul that eateth blood, and will cut him off from among his people. (Leviticus 17:10)
12Therefore I said unto the children of Israel, No soul of you shall eat blood, neither shall any stranger that sojourneth among you eat blood. 13And whatsoever man there be of the children of Israel, or of the strangers that sojourn among you, which hunteth and catcheth any beast or fowl that may be eaten; he shall even pour out the blood thereof, and cover it with dust. 14For it is the life of all flesh; the blood of it is for the life thereof: therefore I said unto the children of Israel, Ye shall eat the blood of no manner of flesh: for the life of all flesh is the blood thereof: whosoever eateth it shall be cut off. 15And every soul that eateth that which died of itself, or that which was torn with beasts, whether it be one of your own country, or a stranger, he shall both wash his clothes, and bathe himself in water, and be unclean until the even: then shall he be clean. (Leviticus 17:12‑15)
; Num. 9:1414And if a stranger shall sojourn among you, and will keep the passover unto the Lord; according to the ordinance of the passover, and according to the manner thereof, so shall he do: ye shall have one ordinance, both for the stranger, and for him that was born in the land. (Numbers 9:14)). Such, if all the males in the family were circumcised, might eat the Passover and offer a burnt offering or sacrifice. The Rabbis say that there were two classes of proselytes.
1. “Proselytes of righteousness,” such as those mentioned above; and
2. “Proselytes of the Gate,” those spoken of as “strangers within thy gates.” The Rabbis also assert that in New Testament times and later the proselytes were received by circumcision and baptism; but it is very much disputed as to when the baptism was added, there being no mention of it in the Old Testament Some hold that it was introduced when the emperors forbade their Gentile subjects to be circumcised, but others think it must have been earlier, which seems confirmed by John 1:2525And they asked him, and said unto him, Why baptizest thou then, if thou be not that Christ, nor Elias, neither that prophet? (John 1:25).
History shows to what an extent proselytizing was abused. The Jews held that on a Gentile becoming a proselyte, all his natural relationships were annulled: he was “a new creature.” Many became proselytes in order to abandon their wives and marry again. This, with other abuses, caused the emperors to interfere; the stricter Jews also were scandalized, and repudiated such proselytes. The Lord describes such a proselyte as the Scribes and Pharisees would make, as “twofold more the child of hell” than themselves (Matt. 23:1515Woe unto you, scribes and Pharisees, hypocrites! for ye compass sea and land to make one proselyte, and when he is made, ye make him twofold more the child of hell than yourselves. (Matthew 23:15)).

Strong’s Dictionary of Greek Words:

from the alternate of 4334; an arriver from a foreign region, i.e. (specially), an acceder (convert) to Judaism ("proselyte")
KJV Usage: