Faulty means broken, flawed, or not working the way it should. A faulty toaster might burn your bread every time, no matter which setting you choose. A faulty lock might stick or fail to open when you turn the key.

The word applies to both physical objects and reasoning. A scientist with faulty logic might draw the wrong conclusions from an experiment because their thinking contains errors. A student's faulty understanding of fractions might lead them to add denominators when they should find a common denominator instead.

When something is faulty, it has a defect or weakness that prevents it from functioning properly. A faulty memory might cause you to remember events differently from how they actually happened. Faulty wiring in a building can create a fire hazard.

Manufacturers sometimes recall products when they discover faulty parts. This protects customers from using something that might fail or cause harm.