Deciduous means falling off at maturity or tending to fall off (deriving from the Latin verb decido, "fall off") and is typically used in reference to trees or shrubs that lose their leaves seasonally and to the shedding of other plant structures such as petals after flowering or fruit when ripe. In a more specific sense deciduous means the dropping of a part that is no longer needed, or falling away after its purpose is finished. In plants it is the result of natural processes. Deciduous has a similar meaning when referring to animal parts such as deciduous antlers in deer, or deciduous teeth, also known as baby teeth, in some mammals (including human children).
Wikipedia at: http://en.wikipedia.org/wiki/Deciduous_tree