Bullet

a bullet was a projectile propelled by a firearm.

At Starfleet Academy, James T. Kirk had learned about the harm bullets caused as they tore through tissue, literally blasting living flesh apart. 

Bullets bounced off dilithium, as it was the hardest known substance in the universe. 

As was the case with many starbases, this one had taken on the personality of the person in charge, and that personality now overlaid the utilitarian Starfleet designs. Hanging at intervals in every corridor were mementos of the nineteenth-century (old calendar) American Wild West. There were paintings of horse soldiers dealing with Native Americans, feathered drums, headdresses many feet long, crossed lances, and framed proclamations announcing the forced movement of various Native American tribes from one part of the old United States to another.

In 2268, Commodore Favere's office on Starbase 12 displayed mementos of 19th century Earth, including brass bullets. 

In 2270, Omne was killed when Kirk fired a bullet into his chest. 

In an alternate timeline, Doctor Georges Mordreaux killed Kirk and Mandala Flynn with bullets fired from a spiderweb gun. Spock was injured when a bullet grazed his temple.