To affix one's signature to.
To write (one's signature).
To approve or ratify (a document) by affixing a signature, seal, or other mark: sign a bill into law.
To hire or engage by obtaining a signature on a contract: signed a rookie pitcher for next season; sign up actors for a tour.
To relinquish or transfer title to by signature: signed away all her claims to the estate.
To provide with a sign or signs: sign a new highway.
To communicate with a sign or signs: signed his approval with a nod.
To express (a word or thought, for example) by sign language: signed her reply to the question.
To consecrate with the sign of the cross.
Bill went to vote and realized that he had not yet signt up for it.