Русско-англо-русский юридический словарь

A side hustle is any type of employment undertaken in addition to one’s full-time job. A side hustle is generally freelance or piecework in nature, providing a supplemental income. Side hustles are often things a person is passionate about, rather day a typical day job worked in order to make ends meet. (Wonolo)

side job. A job undertaken in addition to one's main occupation, as a supplementary source of income: he now has a side job selling newspapers. (Oxford Living Dictionaries)

A side job, also informally called a side hustle or side gig, is an extra job that a person takes in addition to their primary job in order to supplement their income. (Wikipedia)

A man who started making pottery in his garden shed has turned his hobby into a side hustle to run alongside his full-time job. (BBC)