critical angle

Noun

 * 1)  The angle of incidence beyond which light traveling through a medium experiences total internal reflection upon encountering a boundary with a less refractive medium.
 * 2)  The angle of attack beyond which an airfoil stalls, experiencing a decrease in lift and increase in drag due to separation of airflow from the upper surface of the airfoil.
 * 3)  The angle beyond which a ramp or a set of stairs is considered uncomfortable or unsafe.

Translations

 * Arabic: زَاوِيَة حَرِجَة
 * Polish: kąt graniczny
 * Tagalog: maselang siha