fusiform

The word fusiform comes from the Latin words fusus, meaning "spindle," and forma, meaning "shape." It describes a three-dimensional form that is thick in the middle and tapers at both ends—essentially, a rounded spindle. While it isn't a common descriptor for household objects, it is a vital term in biology, medicine, and fluid dynamics.

You'll often encounter "fusiform" when describing biological structures adapted for smooth movement. Many fast-swimming fish and some marine mammals have fusiform bodies that help reduce drag in water. In human anatomy, "fusiform muscles" are muscles with a thick middle and narrower ends. Even the brain uses the term in the name fusiform gyrus, a specific folded region on the underside of the temporal and occipital lobes.

Beyond biology, "fusiform" is a staple in engineering. The "fuselage" of an aircraft is a direct linguistic relative, referring to the spindle-shaped central body of the plane designed to reduce air resistance. Similarly, rocket bodies, torpedoes, and high-performance boat hulls are often described as fusiform to highlight their aerodynamic or hydrodynamic efficiency.

So, while you might not use "fusiform" in casual conversation, it is a precise word for describing something long, rounded, and tapered at both ends, especially in science, medicine, and technical writing.