What term describes a short hairlike process often forming part of a fringe on a cell, used for locomotion?

The correct answer is indeed cilia. Cilia are small, hair-like structures that protrude from the surface of many eukaryotic cells. They play a key role in locomotion, allowing cells to move through fluid environments or to move fluids across the surface of the cell.

Cilia are typically shorter than flagella, another form of cellular appendage, and often occur in large numbers, forming a fringe or brush-like border around the cell. They can beat in coordinated waves, which is essential for their function in propelling the organism or in moving substances across cell surfaces, such as in the respiratory tract where they help clear mucus and particles.

In contrast, flagella are longer and usually present in fewer numbers, primarily serving as a more powerful means of locomotion for certain types of cells, like sperm. Pseudopodia are extensions of the cell body used by some cells for movement and feeding, allowing them to crawl along surfaces. Microvilli, on the other hand, are tiny projections that increase the surface area of cells, particularly in the intestines for nutrient absorption, but they do not provide locomotion. Therefore, the term that best describes a short hairlike process used for locomotion is cilia.