How to say "faulty" in Japanese

• ずさんCommon
  na-adjective, nounCovers 'faulty' in the sense of sloppy or careless — a fault resulting from work done without due care. Suits sloppy workmanship, where the flaw lies in how something was done, not in the thing itself.
  トニーは人ひとを雇やとい、もっと客きゃくを掴つかみ、仕事しごとをより早はやくずさんにやれば、もっと金かねもうけができると思おもったのだ。↗

  Tony realized that if he hired another crew, got more customers and did the job quicker and sloppier, he could make more money.
• 不完全ふかんぜんCommon
  na-adjective, nounCovers 'faulty' as defective or flawed — the thing itself falls short of being whole or working properly. Fits a defective part or system whose fault lies in itself, not in careless handling.
  彼かれの計画けいかくはまだ不完全ふかんぜんな点てんが多おおい。↗

  His plan leaves much to be desired.

Use 「ずさん」 for faults that come from careless, sloppy work, and 不完全 for things that are themselves flawed, defective, or incomplete rather than the product of carelessness.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• ずさんcareless
• 不完全ふかんぜんimperfect
• 穴だらけあなだらけfull of flaws