Convex polyomino
A convex polyomino is a polyomino that is both row-convex and column-convex: that is, it has no vertical or horizontal U-shaped indentations. Considering the boundary word, they are the polyominoes when, going counter-clockwise, you cannot make two right turns in a row. Convex polyominoes have a perimeter equal to their bounding box.
They are a subclass of semiconvex polyominoes.