Substandard Definition

sŭb-stăndərd
sub-standard
adjective
Below standard.
Webster's New World
Of, relating to, or indicating a pattern of linguistic usage that does not conform to that of the prestige group in a speech community or to that of the standard language.
American Heritage
Not in accord with notions of good English; nonstandard.
American Heritage

Of inferior quality; not meeting the minimum quality requirements.

They built this with substandard parts. No wonder it collapsed.
Wiktionary
Synonyms: