IPA: //ʌnˈprɪn.sɪ.pəld//
KK: /ʌnˈprɪn.sə.pəld/
Not having or following moral rules or standards; behaving in a way that is dishonest or unethical.
His unprincipled actions led to a loss of trust among his colleagues.
Unprincipled → It is formed from "un-" (meaning not) and "principled" (from "principle", which comes from Latin "principium", meaning a fundamental truth or proposition). The word "unprincipled" means not adhering to moral principles or lacking a sense of right and wrong.
Think of 'not' ('un-') following a 'fundamental truth' ('principle') — that's why unprincipled describes someone who does not follow moral guidelines.