rib

rib¹

—ribber, n. —ribless, adj. —riblike, adj.

/rib/, n., v., ribbed, ribbing.

n.

1. one of a series of curved bones that are articulated with the vertebrae and occur in pairs, 12 in humans, on each side of the vertebrate body, certain pairs being connected with the sternum and forming the thoracic wall. See diag. under skeleton.

2. a cut of meat, as beef, containing a rib. See diag. under beef.

3. ribs, spareribs (def. 2).

4. Archit.

a. any of several archlike members of a vault supporting it at the groins, defining its distinct surfaces, or dividing these surfaces into panels: including ogives and tiercerons.

b. any of several molded members or moldings, including ridge ribs and liernes, on the surface of a vault accenting the ridges or dividing the surface into panels.

5. something resembling a rib in form, position, or use, as a supporting or strengthening part.

6. a structural member that supports the shape of something: an umbrella rib.

7. Naut. any of the curved framing members in a ship's hull that rise upward and outward from the keel; frame.

8. a stiffening beam cast as part of a concrete slab.

9. a primary vein of a leaf.

10. a vertical ridge in cloth, esp. in knitted fabrics.

11. a ridge, as in poplin or rep, caused by heavy yarn.

12. a wife (in humorous allusion to the creation of Eve. Gen. 2:21-22).

13. Ceram. a scraper for smoothing clay being thrown on a potter's wheel.

14. a metal ridge running along the top of the barrel of a firearm to simplify aligning the sights.

15. a longitudinal strip of metal joining the barrels of a double-barreled gun.

v.t.

16. to furnish or strengthen with ribs.

17. to enclose as with ribs.

18. to mark with riblike ridges or markings.

[bef. 900; ME, OE rib(b); c. G Rippe]

rib²

/rib/, v.t., ribbed, ribbing.

to tease; make fun of.

[1925-30, Amer.; appar. short for rib-tickle (v.)]

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▪ bone

      any of several pairs of narrow, curved strips of bone (sometimes cartilage) attached dorsally to the vertebrae and, in higher vertebrates, to the breastbone ventrally, to form the bony skeleton, or rib cage, of the chest. The ribs help to protect the internal organs that they enclose and lend support to the trunk musculature.

      Fish have two sets of ribs, which attach to the upper and lower parts of the vertebral arches and which do not join in front. The upper (dorsal) set of ribs is believed to have evolved into the ribs of land vertebrates. Attachment of ribs to a breastbone (sternum) to form a rib cage appeared first in reptiles. In the primitive condition, ribs were attached to all vertebrae; this is still true in some reptiles (e.g., snakes), but in mammals only thoracic vertebrae carry ribs. Remnants of cervical ribs secondarily fused to cervical vertebrae (the uppermost part of the vertebral column) are represented by part of the transverse process of the cervical vertebrae.

      The number of pairs of ribs in mammals varies from 9 (whale) to 24 (sloth); of true ribs, from 3 to 10 pairs. In humans there are normally 12 pairs of ribs. The first seven pairs are attached directly to the sternum by costal cartilages and are called true ribs. The 8th, 9th, and 10th pairs—false ribs—do not join the sternum directly but are connected to the 7th rib by cartilage. The 11th and 12th pairs—floating ribs—are half the size of the others and do not reach to the front of the body. Each true rib has a small head with two articular surfaces—one that articulates on the body of the vertebra and a more anterior tubercle that articulates with the tip of the transverse process of the vertebra. Behind the head of the rib is a narrow area known as the neck; the remainder is called the shaft.

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