I love the dictionary.com definition which defines prayer as a spiritual communion (intimacy) with God as in supplication (request), thanksgiving (thanks), adoration (worship), or confession (admission).
Prayer is our way of communicating with our creator. It is an intimate communication. It allows us to request from God those things which we feel as if we are in need of. It permits us to thank God for the things that He has already provided for us. It provides an avenue for us to privately worship God because of who He is. And finally, it allows us to admit to God that we are imperfect creatures who are ever so grateful to have the love, grace, and mercy of a perfectly, marvelous God.
Prayer, however, is not a one-way communication. Prayer is a device, just like a telephone or computer, that allows us to connect to God’s phone line. Because God operates on a heavenly frequency, its a wireless connection; meaning that there are no wires to contend with. There are no answering machines or voice mail so you never have to punch a bunch of numbers to get a connection. There are no busy signals because God’s broadband is beyond anything we can think or imagine. Prayer is a direct line, like the Bat-phone of old, always open for direct communication with an omnipresent God. When we call, God listens; but the key to prayer is that when we listen, God answers.