A little philosophy, a little pragmatics.
In general, what people do is move or transform ‘stuff’. We have some of this stuff and we want it over there, or we have some of this stuff and we want it to be that stuff. In our bodies we do this autonomically (transport chemicals in our blood, convert food to energy). Outside of our bodies, we perform these functions with more volition.
Engineering is doing this with specific purpose. Other disciplines may also do this with purpose – engineers are not unique in that way. Engineering does have its set of methods which differentiate it from other disciplines. It also has some terminology to help practitioners communicate effectively (at least when the terminology is consistent).
So let’s pull these thoughts together.
Engineers develop ‘processes’ and ‘devices’ to manipulate matter, energy and information for a ‘defined purpose’. In engineering terms the defined purpose is captured as scenarios, needs and requirements usually grouped under the heading Requirements. Based on Requirements, engineers use ‘methods’ to analyze the problem space and envision a solution space (Analysis) and then develop the transforms to move matter, energy and information from the source to the sink (Design).