Formation in the mind of the image of an abstract concept. Visualisation derives, in this context, from the graphic representation of variables associated to the concept that one wants to follow. For instance, a plot of the fever vs. time allows us to visualize the evolution of the illness. Fever (temperature) and time are the variables. Illness is the concept.
The practice of imagining a place, person, thing, or event with unusual clarity and intensity. Often it is done in a ritual context and reinforced by repetition.
Concentrating or imagining something very strongly as a visual image. The act of visualising.