one-armed bandit

= fruit machine (fruit).

on-stage, on-the-spot, once, once (and )for all, once a month, once and for all, once for all, once in a while, once more, once upon a time, oncologist, oncoming, one, one after another, one another, one day, one p (also 1p), one's bread is buttered, one's opposite number, one-, one-horse, one-liner, one-man band, one-man show, one-night stand, one-off, one-sided, one-sidedly, one-sidedness, one-time, one-to-one, one-track mind, one-upmanship, one-way, onerous, oneself, ongoing, onion, online, onlooker,