Synonyms for Unprofessional:

adj.

amateur (adjective)
incompetent, nonprofessional, novice, primitive, unskilled, amateur, inexperienced.
improper (adjective)
inadequate, unsuitable, ignorant, unethical.
not done well or skillfully (adjective)
amateur, unethical, inadequate, ignorant, incompetent, inexperienced, amateurish, unsuitable, inexpert.

n.

acting, designate, budding, blue-collar, casual, creative, auxiliary, emeritus, deputy. dilettante, unskillful, ability, dilettantish. unprofessional (noun)
amateurish, unskilled, amateur, inexpert.

Other synonyms:

dilettantish. unskillful. Other relevant words:
amateurish, unskillful, ignorant, dilettantish, inadequate, inexpert, dilettante, unsuitable, unethical.

Usage examples for unprofessional

  1. Don't be so hasty, my dear sir; it's very unprofessional very unprofessional – Caught in a Trap by John C. Hutcheson
  2. He excels, when he tries, in a plain, lucid statement of his subject; as witness, his speech on law reform, in 1828, when, for seven hours, he held the close attention of the unprofessional House of Commons, while he sketched the absurdities and abuses of every branch of the common law, and detailed the amendments he proposed in its principles and administration. – Sketches of Reforms and Reformers, of Great Britain and Ireland by Henry B. Stanton