As a Noun: 1. The salty, colourless liquid that comes out in drops on the surface of your skin when you are hot or frightened. English = sweat. Formal English = perspiration. As a Verb or Adjective: 1. Of a salty, colourless liquid, to come out in drops on the surface of your skin. English = sweat. Formal English = perspire. 2. To be nervous or stressed by a particular situation.