coun·ter·sign
ˈkau̇n-tər-ˌsīn
1
: a signature attesting the authenticity of a document already signed by another
2
: a sign given in reply to another
specifically
: a military secret signal that must be given by one wishing to pass a guard
countersign
transitive verb
coun·ter·sig·na·ture
ˌkau̇n-tər-ˈsig-nə-ˌchu̇r
-chər,
-ˌt(y)u̇r
: the signature of one that countersigns
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Merriam-Webster unabridged



