アルバイト
(Japanese, from German Arbeit, "work")
Frequently abbreviated to baito (バイト), this is the term used in Japan for a part-time or side job (as opposed to the term for a full-time job, which is 仕事, shigoto). Strict rules apply to University students and foreign exchange students in Japan, limiting them to part-time jobs.
Also used to describe second jobs or "moonlighting" by people who already have a full-time job.
Someone holding down an arubaito is termed an arubaitaa (アルバイター, from German Arbeiter, "worker"), although it's just as common to refer informally to the person as a "baito" -- using the term for the job to refer to the person doing it.