A shorthand definition for manifestation might be 'intentional change', or the act of bringing new things, entities or realities into being. It is a product of the creative intentionality that is magic, involving the recombination of existing resources or the generating of new ones - often both at once - to produce a novel outcome. We manifest in order to heal, contribute to and shape the world, to take an active part in creating our lives into being rather than having life happen to us.
Manifestation can be micro or on a movement-level scale. Examples include anything as small but significant as the adoption of a new attitude about a situation or the development of new routines and habits. Larger manifestations might be cultural movements such as the reinvigoration of expertise in indigenous medicine traditions like curandurismo, or herbal healing with plant medicine, and the resurgence of interest in and community around ritualistic hand-poked tattooing traditions from Asia and Polynesia.
Manifestation can be a conscious or a sub-conscious process. We bring things into being whether we intend to or not, and whether or not they effect the change we seek. Of course, we must be careful not to perpetuate the damaging New Age expectation that humans, at the individual level, somehow attract or create their own realities. This obscures and ignores social contexts that strongly condition and constrain us from self-realisation and relational actualisation.
Nonetheless, we can safely say that manifestation works something like a self-fulfilling prophecy - what we feed grows, a practice that adrienne maree brown calls 'attention liberation'. This has been found at the micro-level in neuropsychology, as the neural pathways in the brain that are used most often are revisited again and again. We see it also at the macro-level, as intertwined path dependencies emerge, for example, in technological 'progress' narratives and the neoliberal capitalist political economy.
Less energy is expended using the heavily trodden highways rather than forging new pathways through the jungle, even if those pathways will be better for our well-being over time. This is why it is so important to create situations and settings that support your intentional change, your magic and manifestations. Because humans are meaning making creatures, we must make our own meaning and remind ourselves of it, to reassure us of our direction and keep us upon the right path. Our external lives are a mirror of our internal lives; we need only visit a hoarded house to assure ourselves of that. As without, so within.
Further Resources:
How to Survive the End of the World Podcast: Apocalypse Survival Skill #3: Where There is No Doctor
Tattoo as Ritual Healing Work (Julz Bolinayan)