An occupation, or job, also known as work, was a type of activity that one could perform for money or other benefits.
In 1893, Data was impressed by the bellboy Jack's long list of past occupations. (TNG: "Time's Arrow")
In 2152, Menos described his job for the last twenty years, "hauling spent warp injector casings", as an unpopular but necessary occupation. (ENT: "The Seventh")
In 2268, the M-5 multitronic unit explained its need for survival as being so that man could avoid dying in space or having other dangerous occupations. (TOS: "The Ultimate Computer")
Later that year, Spock's brain was surgically removed yet he remained alive. According to Doctor Leonard McCoy, it was the greatest technical job he had ever seen. Every nerve ending in the brain had been neatly sealed; nothing ripped nor torn, and no bleeding, which he considered a medical miracle. (TOS: "Spock's Brain")
In 2364, upon learning the definition of the term "private eye" from Jean-Luc Picard, Data deemed it to be a most interesting occupation. Picard replied that it probably wasn't really as interesting as literature made it out to be. (TNG: "Lonely Among Us")
Clare Raymond, L.Q. Clemonds, and Ralph Offenhouse's occupations were listed in their files on the SS Birdseye, the space module on which their cryogenically preserved bodies were stored. (TNG: "The Neutral Zone")
In 2377, while being interrogated by Admiral Owen Paris, Leosa stated her occupation as dabo girl. This surprised Reginald Barclay, as she'd claimed to be a teacher previously. (VOY: "Inside Man")
Seven of Nine told Chakotay that she was changing the parameters of their relationship, as they both had dangerous occupations, which she felt would make emotional attachments inadvisable. (VOY: "Endgame")
In 2379, Picard advised the crew of the USS Enterprise-E to be patient, saying that "Diplomacy is a very exacting occupation." (Star Trek Nemesis)