A Boss

1. A swelling, lump or protuberance in an animal, person or object.
2. (geology) A lump-like mass of rock, especially one projecting through a stratum of different rock.
3. A convex protuberance in hammered work, especially the rounded projection in the centre of a shield.
4. (mechanics) A protrusion, frequently a cylinder of material that extends beyond a hole.
5. (architecture) A knob or projection, usually at the intersection of ribs in a vault.
6. (archery) A target block, made of foam but historically made of hay bales, to which a target face is attached.
7. A wooden vessel for the mortar used in tiling or masonry, hung by a hook from the laths, or from the rounds of a ladder.
8. A head or reservoir of water.