A defect is something that makes a product unreasonably dangerous to use as intended.
Three types of “defects”:
Inadequate warnings/marketing defects
When a product does not perform as intended because there was an error or mistake during the manufacturing process then you have a defect in manufacturing. For example, processed food that is contaminated because of a dirty machine.
When a product is used as intended, but still causes injury then you have a defect in design. For example, a machine that does not have any safety guards.
Failure To Warn/Inadequate Warnings
When a manufacturer fails to notify consumers the dangers of using their product then you have a defect in the warnings. For example, a prescription drug that causes heart attacks, but contains no such warning in the label.