boss

1. A lump-like mass of rock, especially one projecting through a stratum of different rock.
2. A convex protuberance in hammered work, especially the rounded projection in the centre of a shield.
3. A protrusion; frequently a cylinder of material that extends beyond a hole.
4. A knob or projection, usually at the intersection of ribs in a vault.
5. A roughly cut stone set in place for later carving.
6. 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.

Plural bosses