1.
bad, defective, faulty
Not meeting the required standard of quality or function. Used for products, conditions, health, and performance.
不良品を交換してもらった。
I had the defective product exchanged.
姿勢が不良だと腰痛の原因になる。
Bad posture can cause lower back pain.
寝不足で体調不良になった。
I became unwell due to lack of sleep.
2.
delinquent, juvenile troublemaker
A young person who engages in antisocial or rebellious behavior. A cultural archetype in Japanese media, especially associated with the stereotypical rebel image of the 1980s and 1990s.
学校の前に不良がたむろしていた。
Delinquents were hanging around in front of the school.
若い頃は不良だったらしい。
Apparently, he was a delinquent when he was young.
不良マンガのブームは1980年代にピークを迎えた。
The boom in delinquent manga peaked in the 1980s.
不良 has two major uses.
Sense 1 (defective/bad) is common in formal and technical contexts:
- 不良品 (defective product)
- 体調不良 (poor health condition)
- 接触不良 (poor contact/loose connection)
- 不良債権 (bad debt, non-performing loan)
Sense 2 (delinquent) refers to a cultural archetype:
- 不良少年/少女 (delinquent boy/girl)
- The stereotypical image includes a modified school uniform, pompadour hairstyle, and motorcycle
- This image is heavily featured in manga and anime genres like {ヤンキー} culture