Noun
A three-way intersection of routes shaped like a capital letter Y.
Synonym: Y-intersection
Coordinate terms: T-intersection, T-junction
A similarly shaped section in a pipe, etc.
Source: en.wiktionary.orgThe intersection of the two faces that are parallel to the observer forms a rectangle, and the lines that converge on the square form a "y-junction" at the two diagonally opposite sides. Source: Internet
If an observer focuses on the upper "y-junction" the lower left face will appear to be in front. Source: Internet