Definition of leaf

• n. - A colored, usually green, expansion growing from the side of a stem or rootstock, in which the sap for the use of the plant is elaborated under the influence of light; one of the parts of a plant which collectively constitute its foliage.
• n. - A special organ of vegetation in the form of a lateral outgrowth from the stem, whether appearing as a part of the foliage, or as a cotyledon, a scale, a bract, a spine, or a tendril.
• n. - 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.
• v. i. - To shoot out leaves; to produce leaves; to leave; as, the trees leaf in May.