a. 1. Having or involving a pressure greatly exceeding that of the atmosphere; -- said of steam, air, water, etc., and of steam, air, or hydraulic engines, water wheels, etc. [ 1913 Webster ]

2. Fig.: Urgent; intense; as, a high-pressure business or social life. [ 1913 Webster ]

3. Using intense psychological pressure or other incentives to convince others to do things; aggressively persistent; as, high-pressure salesmen; high-pressure tactics. [ PJC ]

High-pressure engine, an engine in which steam at high pressure is used. It may be either a condensing or a noncondensing engine. Formerly the term was used only of the latter. See Steam engine. [ 1913 Webster ]