A job is a set of tasks and duties performed, or meant to be performed, by one person, including for an employer or in self employment. Jobs are classified by occupation with respect to the type of work performed, or to be performed.
Source: ILO 2007, Global

A set of tasks and duties carried out or meant to be carried out, by one person for a particular employer, or in self-employment.
Source: SAQA 2013, South Africa

Any employment, full-time or part-time.
Source: Wahba 2013, Global

A set of tasks and duties executed, or meant to be executed, by one person; a regular activity performed in exchange for payment, especially as part of one's trade, occupation, or profession.
Source: TESDA 2010, Philippines

A job here is defined as an occupation in a sector. The two concepts of occupation and sector correspond to two fundamental dimensions of the division of labour within and across organisations. The sector classification designates the horizontal distribution of economic activities across organisations generating different products and services. The occupation classification provides an implicit hierarchy of within-organisation roles– senior managers, line managers, professionals, associate professionals, production staff and so on.
Source: Eurofound 2015, Europe