any rib of the lower two pairs of ribs in humans, which are not attached to the breastbone
floating rib in American English
noun
Anatomy
one member of the two lowest pairs of ribs, which are attached neither to the sternum nor to the cartilages of other ribs
Word origin
[1825–35]This word is first recorded in the period 1825–35. Other words that entered Englishat around the same time include: breakdown, cross section, individualism, relativity, self-help