thorny

形容词 thorny:

1. bristling with perplexities
2. having or covered with protective barbs or quills or spines or thorns or setae etc.
   同义词：barbed, barbellate, briary, briery, bristled, bristly, burred, burry, prickly, setose, setaceous, spiny

1. It's a thorny subject.
   这是个棘手的问题。
2. Cacti are thorny.
   仙人掌多刺。