tantamount

adjective

1. equivalent, as in value, force, effect, or signification: His angry speech was tantamount to a declaration of war.

adjective

1. (postpositive foll by to) as good (as); equivalent in effect (to)his statement was tantamount to an admission of guilt

adj.1640s, from verbal phrase tant amount “be equivalent” (1620s), from Anglo-French tant amunter “amount to as much” (late 13c.), from Old French tant “as much” (from Latin tantus, from tam “so”) + amonter “amount to, go up” (see amount).