A class of trees that have broad, flat leaves of many different shapes; most are deciduous; also called hardwood because most broad-leaved trees have harder wood than do conifers. Examples include oak, hickory, maple and ash. A narrow zone or strip of land, trees or vegetation bordering an area. Common examples include visual buffers, which screen the view along roads, and streamside buffers, which are used to protect water quality. Buffers may also be used to prevent the spread of forest pests.
Medical Definition of id. : the one of the three divisions of the psyche in psychoanalytic theory that is completely unconscious and is the source of psychic energy derived from instinctual needs and drivesâcompare ego, superego.
Definition of ID. 1  1 Idaho. 2  2 identification. 3  3 independent distributor. 4  4 industrial design. 5  5 often not capitalized inside diameter; inner diameter; internal diameter. 6  6 often not capitalized inside dimensions. 7  7 intelligence department.