From: Middle English, from Anglo-French priere, praiere, preiere, from Medieval Latin precaria, from Latin, feminine of precarius obtained by entreaty, from prec-, prex
Date: 14th century
1 a (1): an address (as a petition) to God or a god in word or thought
2: the act or practice of praying to God or a god
Hexham's Concise Dictionary of Religion
Prayer is the means by which an individual or group attempts to enter into verbal or mental communication with a deity.
Prayers can be separated into two categories: prayer with and prayer to. When we are with others, either during a worship service, at a meal, or alongside one who is ill or troubled, we can pray with. Prayer with begins with listening to and caring about those with are with. Our prayers reflect their needs, the matters afflicting their minds and hearts. The purpose of prayer with is to let others know that they have been heard, that they have had the opportunity to articulate their fears, and that they are not alone in their struggles. Prayer with aims to help others find within themselves, their family, and their friends the resources to cope and to explore the wonders of existence.
If one does not believe in a deity, then what is the target of prayer to? We are all part of a universe of forces, fields, and life. We may never comprehend all of the levels of consciousness that exist in that expanse. As constituents in that enterprise, prayer to simply means asking for help from whatever resources there are - whether those resources lie in the depths of time and space, or deep within ourselves.
Atheist Definition: Prayer is the act of engaging spiritually with our inner selves, with others, and with the universe by reaching out and asking for help, support, and reassurance.