1. dangerous; risky; hazardous; perilous; precarious
危ないから前見て歩け。It's dangerous, so watch where you're walking.
2. in danger; in jeopardy; critical; grave; at risk
父の状態が危ないようです。It seems that my father's condition is critical.
3. uncertain; unreliable; insecure; unsteady; doubtful
彼は危ない足取りで階段を下りていった。He went down the stairs with unsteady steps.
4. close (i.e. a close call); narrow
ああ、あれは危なかった。Oh, that was a close call.
5. sketchy; shady; dodgy
often as アブない
あんまり話しかけすぎると、危ない人だと思われちゃうぞ？If you talk to others too much, people will think you're a sketchy person.