having signed, or joined in signing, a document: the signatory powers to a treaty.
noun
2.
a signer, or one of the signers, of a document: France and Holland were among the signatories of the treaty.
Origin: 1640–50, in earlier sense “used in affixing seals”; 1860–65for def 2; < Latinsignātōrius of, belonging to sealing, equivalent to signā(re) to mark, seal (see sign) + -tōrius-tory1
1647, "used in sealing" (adj.), from L. signatorius "of sealing," from signatus, pp. of signare "to sign" (see sign). Noun sense of "one who signs" first recorded 1866.