California Code, Civil Code - CIV § 2784

As used in Sections 2782 and 2782.5, a “design defect” is defined as a condition arising out of its design which renders a structure, item of equipment or machinery or any other similar object, movable or immovable, when constructed substantially in accordance with its design, inherently unfit, either wholly or in part, for its intended use or which impairs or renders the use of such structure, equipment, machinery or property dangerous.