Fusiform (from Latin fusus ‘spindle’) means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a blood vessel.
Examples
Fusiform, a body shape common to many aquatic animals, characterized by being tapered at both the head and the tail[1]
Streamliner, a fusiform hydro-/aero-dynamic vehicle. Historically, the adjective "streamlined" was more commonly used among designers for the word "fusiform".