A speakeasy was a secret bar in the United States in the 1920s and early 1930s, during Prohibition — the years when the law banned making and selling alcohol. People still wanted to drink, so bars went underground: behind an unmarked door, in a basement, at the back of a shop that pretended to sell something else. You often needed to know someone, or say the right word at the door, to get in.

The name tells you the whole story. You had to speak easy — that is, speak quietly, keep your voice down, do not draw attention. The plural is speakeasies.

Here is the part a dictionary line can miss: the word is very much alive today, but with the meaning turned around. A modern 'speakeasy bar' is completely legal. It just copies the style — a hidden entrance, no sign, a dark room, 1920s music, old-fashioned cocktails. Taipei and Taichung have plenty of them, and this is almost certainly where a young person will meet the word first. So when you read it, check the date: 1920s America means the real illegal thing; today it means a bar that is playing dress-up.

Because of the history, the word carries a nice flavour of glamour and secrets rather than of crime, even though the original ones were genuinely against the law.