The breaking down of whole educational qualifications into useful sub-units (modules) each of which has measurable outcomes that are assessed (and in some cases certified) in their own right as well as contributing to a larger overall educational outcome (primarily a qualification).
Source: NCVER 2013, Australia

A system where training content is divided into independent units or modules which can be combined to form a program suited to individual needs, technical developments, or occupational structure, etc., permitting continuous adaptation of the program.
Source: TESDA 2010, Philippines

(Modularisation)A system in which qualifications consist of a number of modules, each of which can be certificated independently. Sometimes, this is known as ‘unitisation’ and ‘modularisation’ is used to refer to a system in which learning programmes consist of a number of components
Source: ILO (SED) 2007, Global