A definition was a statement of the meaning of a word or word group or a sign or symbol.
In 2364, Beverly Crusher stated that there were basic definitions for organic life. (TNG: "Home Soil")
In 2378, Tuvok noted that Section Seven Gamma of the Twelfth Guarantee defined an artist as a person who created an original artistic work. As the Doctor was a hologram and not legally considered a person, Captain Kathryn Janeway noted that the definition of what constituted a person had changed over the centuries and continued to evolve. She asked that the definition be expanded once more to include the Doctor. An arbitrator was later willing to extend the legal definition of artist to include the Doctor and therefore ruled that the Doctor had the right to control his own work. (VOY: "Author, Author")