break out in a sweat

1. To begin sweating suddenly, as from heat, exertion, illness, etc. Barcelona gets so hot in the summer that you break out in a sweat the moment you step outside. I'm so out of shape. I just broke out in a sweat from walking up a single flight of stairs! She broke out in a sweat and then started vomiting. I think she might have food poisoning.

2. To enter a state of fear, anxiety, or worry; to become very nervous or frightened. I broke out in a sweat at the very thought of having to get up in front of an audience. Financial experts are breaking out in a sweat as the market continues to tumble at alarming rates. A: "What's wrong? Why are you breaking out in a sweat?" B: "Because the IRS has been asking questions about our recent finances, that's why!"