IPA: /nɒnˈpɜːfɔːmɪŋ/
KK: /nɑnˈpɜrˌfɔrmɪŋ/
Not working well or not achieving the expected results.
The bank had to deal with several nonperforming loans that were not being paid back.
Nonperforming → It is formed from "non-" (meaning not) and "performing" (from Latin "performare", meaning to carry out or accomplish). The word "nonperforming" describes something that is not carrying out its intended function or task.
Think of 'not' ('non-') doing something 'successfully' ('performing') — that's why nonperforming means not accomplishing its intended purpose.