1 a: the seemingly flat figure of a celestial body <the solar disk>barchaic:discus 2: any of various rounded and flattened animal anatomical structures; especially:intervertebral disk — compare slipped disk 3: the central part of the flower head of a typical composite made up of closely packed tubular flowers 4: a thin circular object: as ausually disc: a phonograph record b: a round flat plate coated with a magnetic substance on which data for a computer is stored cusually disc:optical disk: as (1):videodisc(2):cd 5usually disc: one of the concave circular steel tools with sharpened edge making up the working part of a disc harrow or plow; also: an implement employing such tools