Angle of repose refers to the steepest angle at which a piled substance can remain stable without sliding or collapsing. There are various synonyms for this term, such as tipping point, critical slope, and threshold of stability. Other similar terms include the angle of slide, slope of failure, and failure angle. These words denote the measurement of the point at which the shear stress exceeds the shear strength of the materials. Angle of rest, hillside limit, and slope stability are also words used to describe the angle of repose. Understanding the significance of these synonyms can help in engineering and construction projects, as well as accidents prevention.