Principled means guided by strong beliefs about what's right and wrong, and sticking to those beliefs even when it's difficult or inconvenient. A principled person has a moral compass and follows it consistently.

When your friend finds a wallet full of cash and turns it in to the office instead of keeping the money, that's principled behavior. She knew the right thing to do and did it, even though no one would have known if she'd kept it. When a scientist refuses to falsify research data even though it might make their results look better, they're being principled.

Being principled means your actions match your values. You know right from wrong, and you actually do what you believe is right. A principled student doesn't cheat on tests because they value honesty and learning, whether or not they might get caught. A principled teammate doesn't trash-talk opponents because they believe in treating others with respect, whether or not a coach is watching.

Someone described as principled has thought about what matters to them and lives according to those standards, even when taking the easy way out is tempting.