Products that do not live up to reasonable expectations are defective. A sofa isn't defective because the material used to cover it failed to prevent your dog from chewing up the cushions. Unless the manufacturer guaranteed shred-proof furniture, the sofa is not a defective or unsafe product for failing to withstand an "unreasonable" canine attack.
Product makers may be liable for one of three types of harmful defects. A defective product can be "born bad" by faulty design or may be manufactured improperly, even when a design is fault-free. The third type is a marketing defect with faults in labeling, warnings, instructions or advertising claims -- false promises and harmful omissions included.