I have yet to come across a satisfactory definition for any of the individual words that make up the acronym STEM: science, technology, engineering, and mathematics, so I'd like to offer my own.
Science is preoccupied with the discovery of constraints.
Engineering is preoccupied with working within constraints.
Technology is preoccupied with transcending constraints (with tools).
Mathematics is preoccupied with expressing constraints (with symbols).
All four (4) definitions highlight an important theme that exists across STEM fields: the concept of constraints.
Each definition re-frames, in a handful of words, the four STEM fields as variations on one underlying human endeavor—the human need to deal with constraints.
A side-effect of this re-framing using the concept of constraints is that the definitions are fairly easy to recall–at least for me.