In Washington, what does the law list as unlawful practice of law?
Answered for: Washington
(2) The following constitutes unlawful practice of law: (a) A nonlawyer practices law, or holds himself or herself out as entitled to practice law; (b) A legal provider holds an investment or ownership interest in a business primarily engaged in the practice of law, knowing that a nonlawyer holds an investment or ownership interest in the business; (c) A nonlawyer knowingly holds an investment or ownership interest in a business primarily engaged in the practice of law; (d) A legal provider works for a business that is primarily engaged in the practice of law, knowing that a nonlawyer holds an investment or ownership interest in the business; or (e) A nonlawyer shares legal fees with a legal provider.
The Washington section gives a list rather than a general phrase. The first item covers both practising and holding oneself out as entitled to practise; the others are about ownership of, and fee-sharing with, a law business.
This answer is true in Washington and nowhere else on this site. Another jurisdiction is another answer, or an honest gap: see what has been read for Washington.