b grade

基本解释

Some B-grade movies are very good, but most of them are not worth watching.
有些B级片很不错，不过大多数片子不值得去看。
blog.sina.com.cn
It’s a B-grade slasher directed by John Ottman about a film school where fiction and reality blur.
约翰·欧特曼导演的一部B级恐怖片，故事发生在一所电影学校，在那里，现实与小说的边界模糊了。
Through the analysis, pointed out the key is the wire rod chemical composition is even when produces the B-grade steel wire for cotton packaging.
通过分析，指出在生产B级棉花打包钢丝时，关键是线材的化学成分均匀。化学成分对钢的内部组织、性能及成品质量起决定作用。

Getting a grade like a B-plus or a C-minus adds or subtracts a few tenths of a point.
So my grade if we both put Alpha is B-, if we both put Beta, was B+.
如果我们都选α我得B-,都选β我得B+
耶鲁公开课 - 博弈论课程节选

In Shanghai, for instance, rents this year have increased 18% for grade-A and grade-B buildings in the popular Puxi district as vacancies have fallen to a ten-year low of around 7%, according to Jones Lang LaSalle, a global property consultant.
FORBES: Revolution by Block

A B-grade person or thing is one that you consider to be inferior or of poor quality.