Validation on multiple-words terms

I’m implementing a blacklist with banned terms to be applied on a textarea field. I need to block submissions depending on a criteria defined by the business experts. We cannot find a way to block a term with more than a word (like ‘investment opportunity’). We are using a case insensitive contains criteria for matching, but this term won’t match and forms are still being submitted.
Are there any extra configurations needed for this type of terms?