, um⋅bos. | 1. | a boss on a shield, as one at the center of a circular shield. |
| 2. | any similar boss or protuberance. |
| 3. | Zoology. the beak of a bivalve shell; the protuberance of each valve above the hinge. |
| 4. | Anatomy. the depressed area on the outer surface of the tympanic membrane. |
| 5. | a blunt or rounded protuberance arising from a surface, as on a pine cone scale. |

umbo um·bo (ŭm'bō)
n. pl. um·bos or um·bo·nes (ŭm-bō'nēz)
A small anatomical projection on a surface, such as that on the inner surface of the tympanic membrane at the end of the manubrium of the malleus, corresponding to the most depressed point of the membrane.