1680s, from L. deciduus "that which falls off," from decidere "to fall off," from de- "down" + cadere "to fall" (see case (1)). Originally with reference to leaves, petals, teeth, etc.; specific sense of "trees whose leaves fall off" (opposed to evergreen) is from 1778.
Shedding leaves at the end of a growing season and regrowing them at the beginning of the next growing season. Most deciduous plants bear flowers and have woody stems and broad rather than needlelike leaves. Maples, oaks, elms, and aspens are deciduous. Compare evergreen. See more at abscission.
Falling off or shed at a particular season or stage of growth, as antlers.