RhymeZone: tantamount definitions

Definitions of tantamount:

adjective: Equivalent in meaning or effect; amounting to the same thing in practical terms, even if being technically distinct.
verb: (obsolete) To amount to as much; to be equivalent.
noun: (obsolete) Something which has the same value or amount (as something else). (attributive use passing into adjective, below)

(Definitions from Wiktionary)