1. an abnormal inward curvature of the spine in the lumbar and cervical regions. In extreme cases, the condition is known as hyperlordosis. See also kyphosis; scoliosis.

2. in many rodents, a similar but normal posture that is assumed by females during periods of sexual receptivity and serves to facilitate copulation with a male. In the absence of lordosis, males are physically unable to mate with the female. See presenting.