There is a legal definition: a newly formed business that has not begun its intended normal business activities. Legally, and in the tax code, a "startup" has

There is a legal definition: a newly formed business that has not begun its intended normal business activities. Legally, and in the tax code, a "startup" has various advantages that established businesses do not (i.e., for example, in some states a startup does not pay income taxes for its first year). If you want to add more to the definition...that is a philosophical battle that will never be resolved decisely for any specific extended definition.