Leaf  —n. (pl. Leaves) 1 each of several flattened usu. Green structures of a plant, growing usu. On the side of a stem. 2 a foliage regarded collectively. B state of bearing leaves (tree in leaf). 3 single thickness of paper. 4 very thin sheet of metal etc. 5 hinged part, extra section, or flap of a table etc. —v. 1 put forth leaves. 2 (foll. By through) turn over the pages of (a book etc.).  leafage n. Leafy adj. (-ier, -iest). [old english]