Below the level that is required or accepted — not merely a bit worse than usual, but poor enough that it should not be allowed. An adjective. You hear it most about things that are supposed to meet a rule: substandard housing that is damp and unsafe, substandard building work, substandard care in a hospital, substandard goods that a shop should not have sold. Because of that, it carries a note of blame and often a hint that someone should answer for it, which is why it lives in news reports, inspections, complaints and official documents rather than in casual talk. If your friend cooks a disappointing dinner you would not call it substandard unless you were joking. There is a second, narrower use in language study: 'substandard English' means forms that are not accepted as standard, such as 'he don't'. Be careful with that one — many linguists now avoid it, because calling how real people speak 'substandard' sounds like a judgement on the speakers, and 'nonstandard' is the neutral word they prefer.