As you would expect from the name, this term refers to something that gradually keeps getting bigger and bigger. In a project context, scope creep has occurred when the scope of a service, product or feature has become greater than was originally intended or agreed.
The word “creep” is also similar to "creepy", or scary. Scope creep can be scary for a project, and is something to watch out for.
It can prevent project goals concerning time, cost or benefits from being met. It can often happen gradually and uncontrollably, and is the result of the involvement of different people and/or unclear mandates or decision channels.
Internal drivers can sometimes cause "scope creep", such as developers who want to create what they think is the best solution, or sales staff who encourage the incorporation of added functionality during the process. There may also be external drivers, such as requests from the customer which are incorporated into the project immediately without an established change management process, or checks on what is added to or removed from the backlog.
As an initial step in our projects at Cegal, we want to define the scope as soon as possible, for which we often use a "minimal viable product" or MVP. An MVP defines the least functionality that is actually needed in the earliest versions. This can be a challenging exercise, for both the customer and the supplier, as there is often a lot of functionality that would be nice to have, but including it all could turn out to be both expensive and time-consuming for the project concerned.
The task of a project manager is to communicate any expansions to the stakeholders involved and provide anchoring. If functionality is added to an MVP or backlog, the project manager must also explain the possible consequences as regards the project's timeline. A good rule of thumb in a project is to have an active attitude towards the MVP from start to finish, and to ask the question: what is good enough?