From BiblePortal Wikipedia

Vine's Expository Dictionary of OT Words [1]

A. Verb.

Pâlal ( פָּלַל , Strong'S #6419), “to pray, intervene, mediate, judge.” Found in both biblical and modern Hebrew, this word occurs 84 times in the Hebrew Old Testament. The word is used 4 times in the intensive verbal form; the remaining 80 times are found in the reflexive or reciprocal form, in which the action generally points back to the subject. In the intensive form pâlal expresses the idea of “to mediate, to come between two parties,” always between human beings. Thus, “if a man sins against a man, God will mediate for him …” (1 Sam. 2:25, RSV). “To mediate” requires “making a judgment,” as in Ezek. 16:52: “Thou also, which hast judged thy sisters.…” In the remaining 2 references in which the intensive form is used, pâlal expresses “making a judgment” in Gen. 48:11 and “coming between” in Ps. 106:30.

The first occurrence of pâlal in the Old Testament is in Gen. 20:7, where the reflexive or reciprocal form of the verb expresses the idea of “interceding for, prayer in behalf of”: “… He shall pray for thee.…” Such intercessory praying is frequent in the Old Testament: Moses “prays” for the people’s deliverance from the fiery serpents (Num. 21:7); he “prays” for Aaron (Deut. 9:20); and Samuel “intercedes” continually for Israel (1 Sam. 12:23). Prayer is directed not only toward Yahweh but toward pagan idols as well (Isa. 44:17). Sometimes prayer is made to Yahweh that He would act against an enemy: “That which thou hast prayed to me against Sennacherib king of Assyria I have heard” (2 Kings 19:20).

Just why this verb form is used to express the act of praying is not completely clear. Since this verb form points back to the subject, in a reflexive sense, perhaps it emphasizes the part which the person praying has in his prayers. Also, since the verb form can have a reciprocal meaning between subject and object, it may emphasize the fact that prayer is basically communication, which always has to be two-way in order to be real.

B. Noun.

Tephillâh ( תְּפִלָּה , Strong'S #8605), “prayer.” This word, which appears 77 times in biblical Hebrew, is the most general Hebrew word for “prayer.” It first appears in 1 Kings 8:28: “Yet have thou respect unto the prayer of thy servant, and to his supplication.…” In the eschaton God’s house will be a house of “prayer” for all peoples (Isa. 56:7); it will be to this house that all nations will come to worship God. The word can mean both a nonliturgical, non-poetical “prayer” and a liturgical, poetical “prayer.” In the latter special meaning tephillâh is used as a psalm title in 5 psalms and as the title of Habakkuk’s prayer (Hab. 3:1). In these uses tephillâh means a prayer set to music and sung in the formal worship service. In Ps. 72:20 the word describes all the psalms or “prayers” of Psalms 1- 72, only one of which is specifically called a “prayer” (17:1).

King James Dictionary [2]

Pray, L precor proco this word belongs to the same family as preach and reproach Heb. to bless, to reproach rendered in  Job 2.9 , to curse properly, to reproach, to rail at or upbraid. In Latin the word precor signifies to supplicate good or evil, and precis signifies a prayer and a curse. See Imprecate.

1. To ask with earnestness or zeal, as for a favor, or for something desirable to entreat to supplicate.

Pray for them who despitefully use you and persecute you.  Matthew 5

2. To petition to ask, as for a favor as in application to a legislative body. 3. In worship, to address the Supreme Being with solemnity and reverence, with adoration, confession of sins, supplication for mercy, and thanksgiving for blessings received.

When thou prayest, enter into thy closet,and when thou hast shut thy door, pray to thy Father who is in secret, and thy Father who seeth in secret, shall reward thee openly.  Matthew 6

4. I pray, that is, I pray you tell me, or let me know, is a common mode of introducing a question.

PRAY, To supplicate to entreat to urge.

We pray you in Christ's stead, be ye reconciled to God.  2 Corinthians 5

1. In worship, to supplicate to implore to ask with reverence and humility.

Repent therefore of this thy wickedness, and pray God, if perhaps the thought of thy heart may be forgiven thee.

 Acts 8 .

2. To petition. The plaintiff prays judgment of the court.

He that will have the benefit of this act, must pray a prohibition before a sentence in the ecclesiastical court.

3. To ask or intreat in ceremony or form.

Pray my colleague Antonius I may speak with him.

In most instances, this verb is transitive only by ellipsis. To pray God, is used for to pray to God to pray a prohibition, is to pray for a prohibition, &c.

To pray in aid, in law, is to call in for help one who has interest in the cause.

Webster's Dictionary [3]

(1): ( v. t.) To effect or accomplish by praying; as, to pray a soul out of purgatory.

(2): ( v. t.) To ask earnestly for; to seek to obtain by supplication; to entreat for.

(3): ( v. t.) To address earnest request to; to supplicate; to entreat; to implore; to beseech.

(4): ( v. i.) To make request with earnestness or zeal, as for something desired; to make entreaty or supplication; to offer prayer to a deity or divine being as a religious act; specifically, to address the Supreme Being with adoration, confession, supplication, and thanksgiving.

(5): ( n. & v.) See Pry.