Which term describes a shape that is similar to a sword?

The term that describes a shape similar to a sword is "xiphoid." This term is often used in anatomy to refer to the xiphoid process, which is a small, sword-like structure at the lower end of the sternum. The shape of the xiphoid process resembles that of a sword, tapering at one end, which is a defining characteristic of this term.

The other options do not relate to sword-like shapes. A trapezoid refers to a four-sided figure with at least one pair of parallel sides; a pentagon is a five-sided polygon; and a roundoid describes something that is circular or rounded in shape. None of these terms imply a resemblance to a sword.