The Collaborative International Dictionary
Pons \Pons\, n.; pl. Pontes. [L., a bridge.] (Anat.) A bridge; -- applied to several parts which connect others, but especially to the pons Varolii, a prominent band of nervous tissue situated on the ventral side of the medulla oblongata and connected at each side with the hemispheres of the cerebellum; the mesocephalon. See Brain.
Pons asinorum. [L., literally, bridge of asses.] See Asses' bridge, under Ass.
WordNet
n. a problem that severely tests the ability of an inexperienced person
Wikipedia
In geometry, the statement that the angles opposite the equal sides of an isosceles triangle are themselves equal is known as the pons asinorum (; ), Latin for "bridge of donkeys". This statement is Proposition 5 of Book 1 in Euclid's Elements, and is also known as the isosceles triangle theorem. Its converse is also true: if two angles of a triangle are equal, then the sides opposite them are also equal.
The name of this statement is also used metaphorically for a problem or challenge which will separate the sure of mind from the simple, the fleet thinker from the slow, the determined from the dallier; to represent a critical test of ability or understanding.'
Usage examples of "pons asinorum".
Every schoolboy knows that the Pons Asinorum is not to be crossed except by two white donkeys led by a blind man.
For this preliminary training of the brain is the Pons Asinorum of the whole process.
Remember Socrates' slave who worked out the pons asinorum with a stick in the sand?