The idiomatic English phrase, “in full swing,” refers to something that is in active motion, established, or in active progress. This phrase can apply to physical objects or intangible processes. There is a more technical definition and several colloquial ones based on different metaphors for the physical activity of swinging.
Some of the more technical definitions for “in full swing” include a description of someone who is swaying back and forth. This phrase can also describe inanimate objects which are swinging back and forth from some applied motion. Here the phrase is used more literally to actually describe the physical process, such as a pendulum, or even a child's swing.
Another definition for in “full swing” refers to music. A band that is in the middle of a rhythmic song can be said to be in full swing. This designation generally refers to music that is rhythmically consistent and in its higher tempo moments or more filled out instrumental phases.
Other uses of “in full swing” relate to intangible processes. For example, someone who is looking at a volatile market could describe “swinging” stock prices that are increasing or decreasing quickly. Here the processes of increasing or decreasing, especially as they are represented on a chart, can be similar to a swinging motion. When the stock market is fluctuating largely in either direction, an observer could say that it is “in full swing.”
Besides this largely literal phrase, some other alternatives can be used to talk about something that is swinging or moving rapidly, widely, or significantly. Some English speakers might also say that someone or something is “swinging all over the place” or “swinging wildly.” Some more descriptive speakers might say that something or something is “swinging like the devil,” which is based on a wider set of idioms around the idea of “the devil” in Judeochristian religion. Others might say that a person or object is “swinging around like crazy"; here, the word “around” represents the general significance of the motion, and “like crazy” described the motion as exaggerated or more extreme than usual.