In quality management and manufacturing engineering, LSL stands for Lower Specification Limit, representing the absolute lowest boundary or minimum acceptable value that a product characteristic or process measurement can have while still meeting customer and engineering requirements. If a measured variable falls below the Lower Specification Limit, the item is classified as defective or non-conforming. Quality control professionals utilize LSL alongside the Upper Specification Limit (USL) to calculate process capability indices like Cp and Cpk, ensuring that manufacturing variation remains safely within acceptable engineering tolerances.