undersign

[ uhn-der-sahyn, uhn-der-sahyn ]
/ ˌʌn dərˈsaɪn, ˈʌn dərˌsaɪn /

verb (used with object)

to sign one's name under or at the end of (a letter or document); affix one's signature to.

Origin of undersign

First recorded in 1570–80; under- + sign
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019