IPA: /nɒn.kənˈvɛn.ʃən.əl/
KK: /nɑnˈkənˈvɛnʃənl/
Not following the usual or traditional ways of doing things; different from what is generally accepted.
Her nonconventional approach to problem-solving often leads to innovative solutions.
Nonconventional → It is formed from "non-" (meaning not) and "conventional" (from Latin "conventionem", meaning agreement or assembly). The word "nonconventional" means not adhering to established conventions or norms.
Think of 'not' ('non-') following the usual 'agreement' ('conventional') — that's why nonconventional means not following the usual ways.