It also used to refer to the natural angle ( above horizontal ) of the side of a cone shape of loose material poured directly from above ( ie a heap of coal )
Ants that enter the pit trap scramble with poor footing to escape, while the larvae at the bottom of the pit lobs grains of sand at the intended prey. Poor purchase results from the fact that the ant lion's trap walls are exactly at the angle of repose for the material. So the ant or other bug scrambling up the trap wall is at a huge disadvantage. The lobbing of sand grains further dislodges the trap wall grains above the scrambling ant.
It also used to refer to the natural angle ( above horizontal ) of the side of a cone shape of loose material poured directly from above ( ie a heap of coal )
Yes, the term has multiple meanings. But the context of mechanics was clear.