New position category

I believe there should be a new positional category in addition to "pin" and "skewer" called "locked". For example, in the position given below, the black bishop is not pinned, it is not skewered, and it is not trapped, but it is "locked". If it moves, it's checkmate (which is what happened...) 

Just wondering, is this position also incorporated under the term "pinned"? 

I would say yes. The bishop isn't pinned to a piece but to a square. Most motifs can target squares as well as pieces.

Technically speaking it doesn't fit the definition of "pin."

"In chess, a pin is a situation brought on by an attacking piece in which a defending piece cannot move without exposing a more valuable defending piece on its other side to capture by the attacking piece" (Wikipedia).

From that same wikipedia article:

"Sometimes in a chess game position, a piece may be considered to be in a situational pin. In a situational pin, moving the pinned piece out of the line of attack will result in a situation detrimental to the player of the pinned piece, such as a checkmate. Although a situational pin is not an absolute pin and the pinned piece can still be moved according to the rules, moving out of line of attack can result in a bad situation or even immediate loss of the game."

looks like an X-ray, no?

Thanks Martin. Yes, I suppose this must be a situational pin.