In order to be an effective designer, I find it appropriate, if not essential, to sketch out a definition of the word design as I understand it.

1. The word design is primarily a verb. The noun form of design refers exclusively to the act of designing. The artifacts left behind by designing are instead called forms. Not every form is designed. Rather, most are not.
2. Designing is a process, indeed an act. Acts require agents — in this case, the designer.
3. The designer must possess enough capacity of memory and projection to act with purpose and define an objective as part of the process of design. To design is therefore more than to respond directly to stimuli, though great intelligence on the part of the designer may not be necessary to perform rudimentary design.
4. The objective the designer seeks must be known, by both the designer and by onlookers, in order to steer the process and evaluate its results.
5. The objective the designer seeks must be augmentative — that is, it must seek a surplus. Design cannot be performed under duress. As well, acting with a goal of mere survival or subsistence is not designing: it is engineering, because in those cases the requisite form and context are both well-defined.
6. The objective the designer seeks must also be substantive — that is it must yield something of demonstrable utility. Although the designer may be the sole beneficiary, the utility of the result must be understandable by others. Otherwise, it is art.
7. The designer must consider the ensemble of both the context — the part of the world that is not to be changed, and the form — the part of the world that is. The designer must define this ensemble and produce a form that fits the context.

Therefore:

Design is the conspicuously deliberate act of framing a context and fitting to it a complementary form that substantively augments its beneficiaries.

Or, more colloquially:

Design is something we humans do when we aren't being chased by predators.