The Tate Modern Gallery in London defines Generative art as:
Generative art is art made using a predetermined system that often includes an element of chance – is usually applied to computer based art.
Wikipedia defines it as follows:
Generative art refers to art that in whole or in part has been created with the use of an autonomous system. An autonomous system in this context is generally one that is non-human and can independently determine features of an artwork that would otherwise require decisions made directly by the artist. In some cases the human creator may claim that the generative system represents their own artistic idea, and in others that the system takes on the role of the creator.
AIArtists.org defines it as:
Generative Art is a process of algorithmically generating new ideas, forms, shapes, colors or patterns. First, you create rules that provide boundaries for the creation process. Then a computer (or less commonly a human) follows those rules to produce new works.
In contrast to traditional artists who may spend days or even months exploring one idea, generative code artists use computers to generate thousands of ideas in milliseconds. Generative artists leverage modern processing power to invent new aesthetics – instructing programs to run within a set of artistic constraints, and guiding the process to a desired result.
Wikipedia defines creative coding as follows:
Creative coding is a type of computer programming in which the goal is to create something expressive instead of something functional. It is used to create live visuals and for VJing, as well as creating visual art and design, entertainment, art installations, projections and projection mapping, sound art, advertising, product prototypes, and much more.