Something which is like a leaf in being wide and thin and having a flat surface, or in being attached to a larger body by one edge or end; as : (a) A part of a book or folded sheet containing two pages upon its opposite sides. (b) A side, division, or part, that slides or is hinged, as of window shutters, folding doors, etc. (c) The movable side of a table. (d) A very thin plate; as, gold leaf. (e) A portion of fat lying in a separate fold or layer. (f) One of the teeth of a pinion, especially when small.