Slightly Unacceptable product: it refers to the unit product that has one more general or slight defects, but without fatal or severe defects.

At the casing factory, the foreman showed us an example of a product he had made that he deemed to be of unacceptable quality.

Lester: I'm afraid that's unacceptable. Your contract says that you will deliver a product with a reject rate of less than five percent.