专业很冷门怎么说英语

If you want to say that a profession is not very popular or well-known in English, you can use the phrase "niche profession" or "obscure profession." Here are a few examples:
"My profession as a rare book dealer is definitely a niche profession. Not many people know about it."
"I'm studying to become a paleontologist, which is an obscure profession. It's not something that a lot of people are interested in."
Alternatively, you could use the phrase "unconventional career" to describe a profession that is not mainstream or typical:
"I'm pursuing an unconventional career as a glassblower. It's not a job that many people think of as a career choice."
You could also use the phrase "offbeat profession" to describe a profession that is not mainstream or typical:
"I'm considering going into an offbeat profession as a beekeeper. It's not something that a lot of people do, but I find it really interesting."