Define slot machine: a machine used for gambling that starts when you put coins into it and pull a handle or press a button. Reset slot machines after payoffs. Make repairs or adjustments to slot machines or recommend removal of slot machines for repair. Report hazards and enforce. Top Definition. Slot Machine. A coin-operated device, used by low-lifes, cretins, old ladies with blue hair, and idiots who like ringing bells and flashing lights. Although the original slot machine used five reels, simpler, and therefore more reliable, three reel machines quickly became the standard. Retrieved 10 July Likewise, a seven is not any bar, so a combination such as bar-seven-double bar pays. The prototype was mounted in a full size show-ready slot machine cabinet. They "sought to show that these "losses disguised as wins" LDWs would be as arousing as wins, and more arousing than regular losses". This is known as the "theoretical payout percentage" or RTP, "return to player".