To attack someone or something, usually used as a command to a dog: "When her neighbor saw the stranger trying to break into his house, he told the thief to stand still or he would sic his dog on him."

To indicate that the spelling or wording of something is intentional or original: "The editor wrote sic in the margins of the copy so the typesetter would understand that any misspellings or misuses of any words were intentional because they were written that way by another writer who was being quoted exactly."

1. Not well, being ill, feeling queasy, or being nauseated: "He had a sick feeling all day and so he was not able to do any work on the project."
2. Corrupt in a spiritual or moral sense: "His sense of humor was vulgar and no one laughed at his sick jokes."
  3. Filled with anxiety: "She was sick with worry before her daughter finally came home late from school."
4. Emotionally unsound or disordered: "Her mind was sick and she had to be psychologically treated for several months."