The phrase "natural curve" refers to the shape or form that something naturally takes. It means that without any artificial or forced intervention, an object or body part has a curved or bent shape. Full definition
This mattress feels like a cloud and adjusts to the contours and natural curves of your child's body to give them a completely customizable and comfortable sleep. (earlymomentsmatter.org)
The proper push - up pose is in fact very similar to the proper standing posture, with natural curve in the lumbar spine. (fitnessandpower.com)
Natural curved wood branches are the base of this beauty. (chairish.com)