Meaning of "life": the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death.
As for the purpose of life: Life has no purpose, because life is purpose of other purposes, and has highest value of all things.
For the people who are interested in The Law of Complexity/Consciousness. The Law of Complexity/Consciousness is the postulated tendency of matter to become more complex over time and at the same time to become more conscious. The law was first formulated by Jesuit priest and paleontologist Pierre Teilhard de Chardin.
Teilhard holds that at all times and everywhere, matter is endeavoring to complexify upon itself, as observed in the evolutionary history of the Earth. Matter complexified from inanimate matter, to plant life, to animal life, to human life. Or, from the geosphere, to the biosphere, to the noosphere (of which humans represented, because of their possession of a consciousness which reflects upon themselves). As evolution rises through the geosphere, biosphere, and noosphere, matter continues to rise in a continual increase of both complexity and consciousness.
For Teilhard, the Law of Complexity/Consciousness continues to run today in the form of the socialization of mankind. The closed and circular surface of the Earth contributes to the increased compression (socialization) of mankind. As human beings continue to come into closer contact with one another, their methods of interaction continue to complexify in the form of better organized social networks, which contributes to an overall increase in consciousness, or the noosphere.
Teilhard imagines a critical threshold, the Omega Point, in which mankind will have reached its highest point of complexification (socialization) and thus its highest point of consciousness. At this point consciousness will rupture through time and space and assert itself on a higher plane of existence from which it can not come back.
In Teilhard's view, because the Law of Complexity/Consciousness runs everywhere and at all times, and because of the immensity of both time and space and the immensity of the chances for matter to find the right conditions to complexify upon itself, it is highly probable that life exists, has existed, and will exist in the universe apart from our Earth.