the activity of exerting your muscles in various ways to keep fit
"the doctor recommended regular exercise"
"he did some exercising"
"the physical exertion required by his work kept him fit"
An exercise session; a period of physical exercise.
"I went to the gym early in the morning to complete my daily workout before heading to work."
In plain English: A workout is an exercise session where you do physical activity to get stronger or fitter.
"I go to the gym for an hour-long workout every morning before work."
Usage: Use workout to refer specifically to the time spent exercising, such as going to the gym or doing yoga at home. It is often confused with exercise, which can describe either the activity itself in general or a single set of movements within that session.
The word workout comes directly from combining the verb phrase to work with out. Originally meaning to exercise until one is exhausted or finished a specific task, it entered English as a noun describing that physical activity itself.