1. Cross; to place a sign on or mark by signs; to represent or indicate by a sign
2. To affix a signature to; ratify or attest by hand or seal; to assign or convey formally; to write down (one's name); to affix one's name to
3. To communicate by making a sign or by sign language
4. To engage or hire by securing the signature of on a contract of employment — often used with up or on
5. To write one's name in token of assent, responsibility, or obligation
6. To make a sign or signal; to use sign language
To sign at the bottom of (a document, for example).