What Is Work? Definition, Formulas, and Units. In Physics, the term work is used in relation to the displacement produced by the force. WORK definition: 1. an activity, such as a job, that a person uses physical or mental effort to do, usually for…. Learn more. The meaning of WORK is to perform work or fulfill duties regularly for wages or salary. How to use work in a sentence. Synonym Discussion of Work. Learn the meaning of work as a noun and a verb in English, with different senses and usage. Find out how to use work in phrases, idioms, and grammar rules.