1. Of an activity or action, to be dangerous or likely to fail. English = (be) risky , (be) hazardous, (be) perilous.
2. To be unsure about something. English = (be) doubtful.
3. To be in a condition or situation where something unpleasant might happen to you. English = (be) at risk.
4. To be weak and easily hurt physically or emotionally. English = (be) vunerable.
5. To do something that involves a risk of failure because it is new and different. English = venture.