Meaning:
A geographical term, “天坑” literally means “sinkhole,” a hole in the ground that forms when water dissolves surface rock. Often, this surface rock is limestone, which is easily eroded by the movement of water. In metaphor, this term refers to something that poses a danger or threat, like a trap. “专业” refers to “majors in universities.” Chinese use the term “天坑专业” to refer to “biology, chemistry and material science majors,” because they take a lot of effort to learn and often lead to jobs in hazardous environments that are not well compensated.
Example:
A: 你儿子决定在大学里学什么专业？
Nǐ érzi juédìng zài dàxué lǐ xué shénme zhuānyè？
What major has your son decided to choose in the university?
B: 他喜欢化学，著名的天坑专业。
Tā xǐhuān huàxué，zhùmíng de tiānkēng zhuānyè。
He likes chemistry, a major well-known as an entrapment.