lordosis

noun

1. (countable, uncountable)The normal concave, backwards curvature of the spine in the cervical and lumbar regions.
2. (countable, uncountable)An abnormal excessive concave, backwards curvature of the spine, causing in normal human physiology a hollow in the back (lumbar lordosis, hollow back, saddle back) or the neck (cervical lordosis).
3. (countable, uncountable)A body posture of some female mammals, indicating receptivity to copulation. It involves lowering of the forelimbs but with the rear limbs extended and hips raised, ventral arching of the spine and a raising, or sideward displacement, of the tail.