IPA: //sʌbˈævərɪdʒ//
KK: /sʌbˈævərɪdʒ/
Describing something that is lower than the average level or standard.
His performance in the test was subaverage compared to his classmates.
Subaverage → It is formed from "sub-" (meaning under or below) and "average" (from Old French *averagier*, meaning to assess or evaluate). The word "subaverage" means below the average or less than the typical standard.
Think of being 'under' ('sub-') the typical standard of quality or performance, which is what 'subaverage' means.