No. "Underskrive" is a verb, and it can only mean to place your signature on a piece of paper. It literally translates as "underwrite" Then there's "sign", used as a noun ("it's a good sign"/"that's a sign of quality" etc.), which is "tegn" in Danish. So sign language is "tegnsprog". Finally, there's a sign on a shop or a highway, which is called "skilt" in Danish.