When something is tantamount to another thing it is essentially its equivalent. For some animal activists, wearing fur is tantamount to murder.

Tantamount often refers to an action or thing being compared to another greater action or quality, as in, “Missing your finals is tantamount to dropping out of college.” While the two sides are essentially equal, you would not say, “Dropping out of school is tantamount to missing your finals.” A related word is paramount, which means “the highest” or “primary.”