A bogaz is a very specific type of gorge or canyon. It is, in essence, a very large grike, or a rather small polje. It usually originates at a ponor.
For those of us that prefer to have our geological formations in English, a bogaz is a type of formation found in karst topology in which the rock (usually limestone) was eaten away along a joint to form a long, narrow cleft or ravine. They often have steep, almost vertical sides. This is exactly the same thing as a grike, except bigger. The exact dimensions that constitute as a grike vs. a bogaz are vague, but generally, if it's big enough for you to stand comfortably in, it's probably best referred to as a bogaz. Sometimes the upper limit is given as 4-5 meters deep and tens of meters long; other sources go up to 50 meters deep and over a kilometer long. Larger valleys carved out of limestone are usually called polje.
Bogaz is a Slavic word. While it is commonly used in English (by geologists, anyway), the Spanish word zanjon is sometimes also used. If you wish to stick fanatically to English, you might refer to a bogaz as a 'karst corridor' or 'karst street' -- but of course, 'karst' also comes to us from the Slavic.
References:
Fundamentals of Geomorphology by Richard J. Huggett
http://www.speleogenesis.info/index.php