L
shaped polygon name

Yes, it's a hexagon, specifically a non-convex hexagon on account of having a concave angle. There's no specific official name that I'm aware of. "L-shaped hexagon" might actually be sufficient.

Explanation:

One answer is a right-angled concave hexagon, but you do need to cite some context. – Andrew Leach♦ Sep 8 '15 at 9:53. Well... since the Greek letters "gamma" and "lambda" are shaped roughly like the letter "L," you might call it "gammoid" or "lambdoid." I just invented these words.

not clear