The expression "was tantamount to" essentially means to be equivalent or alike in different terms. Some alternatives for this phrase include using phrases such as "was comparable to" or "was essentially the same thing as." Other synonyms for "was tantamount to" may include "was tantamount in value," "was equal to," or "was parallel to." Ultimately, these phrases indicate that whatever is being discussed is in some way the same as another thing in terms of importance, worth, or relevance. By utilizing synonyms for "was tantamount to," writers can more effectively convey their points while avoiding repetitive language.