A malfunction or breakdown was the unintended partial or total loss of or alteration of functionality in a system.
In 2366, after a series of malfunctions on the USS Enterprise-D, Captain Jean-Luc Picard believed that they were dealing with a potential breakdown of the main computer, but according to Lieutenant Commander Data, the system automatically provided for self-correction and there had not been a systems-wide technological failure on a starship in seventy-nine years. (TNG: "Evolution")
Types of malfunctions
In 2366, the Enterprise's launch of "The Egg" probe was interrupted by an instability of the ship. The Enterprise was unresponsive, preventing Ensign Wesley Crusher from stabilizing it, and the ship's inertia dampeners became unresponsive and unable to be reset by Geordi La Forge. However, La Forge was able to reverse impulse engines, but the ship's momentum carried them into the path of stellar matter. After impact, Data reported that all systems were functioning normally and the ship's computer noted that no control malfunction had been recorded. (TNG: "Evolution")
Environmental system malfunction
An environmental system malfunction was the malfunction of life support systems.
A transporter malfunction or transporter accident was a malfunction in a transporter system that could have a wide variety of effects from transporting to an unintended destination, alterations to the transported subject, and even death.