\Tan"ta*mount`\, a. [F. tant so much (L. tantus) + E.
amount.]
Equivalent in value, signification, or effect.
      A usage nearly tantamount to constitutional right.
                                               --Hallam.
      The certainty that delay, under these circumstances,
      was tantamount to ruin.                  --De Quincey.

\Tan"ta*mount`\, v. i.
To be tantamount or equivalent; to amount. [Obs.] --Jer.
Taylor.