How do we define prayer?
A document called the Westminster Shorter Catechism lists answers to theological questions, including Question 98:
Q: What is prayer?
A: Prayer is (1) an offering up of our desires unto God, (2) for things agreeable to his will, (3)in the name of Christ, (4) with confession of our sins, (5) and thankful acknowledgment of his mercies.
(1) Psalm 62:8. Trust in him at all times; ye people, pour out your heart before him: God is a refuge for us. Selah.
Psalm 10:17. Lord, thou hast heard the desire of the humble: thou wilt prepare their heart, thou wilt cause thine ear to hear.
(2) 1 John 5:14. And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us.
Matthew 26:39. And he went a little further, and fell on his face, and prayed, saying, O my Father, if it be possible, let this cup pass from me: nevertheless not as I will, but as thou wilt.
John 6:38. For I came down from heaven, not to do mine own will, but the will of him that sent me.
(3) John 16:23. And in that day ye shall ask me nothing. Verily, verily, I say unto you, Whatsoever ye shall ask the Father in my name, he will give it you.
(4) Daniel 9:4. And I prayed unto the Lord my God, and made my confession, and said, O Lord, the great and dreadful God, keeping the covenant and mercy to them that love him, and to them that keep his commandments.
(5) Philippians 4:6. Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.