Board Thread:Questions and Answers/@comment-24154478-20160704100912/@comment-25600444-20160704101611

If you mean a card like;

Abygale "SD"

Then it stands for Super Deformed.

It comes from this. Basically, you take one character, chibi-fy them, then make some parts bigger or more pronounced then usual.

For example, many refer to Abygale's SD form as "Penguin Dragon" becuase his "arms" look like Penguin Flippers.