Designing is habitable sculpture. A fifty character minimum only leads to verbosity. So to meet the minimum I would add that habitable sculpture can be a building, structure, or landscape to experience.
Designing is the art and science of dynamic in theory and practice of design, erection, commission, maintenance, management and co-ordination of allied professional inputs such as architect, civil and structural engineer, surveyors, mechanical engineer and electrical engineers, thereto of building or part thereof and lay-out and master plans of building or group of building forming a comprehensive institutions, establishment or neighborhood as well as organized spaces required for human and any other structural activities.