n. A small thick lump.n. A piece or plug of tobacco.n. A bar of wood or metal used to support or steady anything.n. Nautical: A square bar of wood or iron, with a shoulder at one end, used to support a topmast or topgallantmast when swayed up into place. The fid passes through a square hole in the heel of its mast, and its ends rest on the trestletrees.n. A conical pin of hard wood, from 12 to 24 inches long, and from 1 to 3 inches in diameter at the butt, used to open the strands of rope in splicing.Nautical, to sway into place and secure (a topmast or topgallantmast) by its fid. Also fidd.