Synonyms for Amateurish:

adj.

all (adjective)
inexpert, unskilled, amateur.
unprofessional (adjective)
inept, inexpert, incompetent, bush-league, unskilled.
unskillful (adjective)
awkward, incompetent, unpolished, inept, unpracticed, unskillful, Skill-less, crude.

n.

helpless, no-good, incapable, someone couldn't do something if they tried, awful, poor. dilettante, dilettantish, nonprofessional, ability. amateurish (noun)
inexpert, unprofessional, unskilled, amateur.
crude (noun)
bush-league.

Other synonyms:

dilettantish. Other relevant words:
dilettante, nonprofessional, unskilled, dilettantish, helpless, unprofessional, amateur, awful, bush-league, poor, inexpert.

Usage examples for amateurish

  1. Mrs. Hardy, who, during her husband's lifetime had never found it necessary to bear financial responsibilities or make business decisions, was an amateurish buyer, her tendency being alternately to excess of caution on one side and recklessness on the other. – The Cow Puncher by Robert J. C. Stead
  2. " Drivenny is the great jewel expert," Haslemere condescended to enlighten my amateurish intelligence. – Lord John in New York by C. N. Williamson A. M. Williamson
  3. I could not talk with Anazeh very well, because when he tried to understand my amateurish Arabic and to modify his flow of stately speech to meet my needs, he always put his head down, and the helm with it. – Jimgrim and Allah's Peace by Talbot Mundy