This entry is about the noun in the fixed phrase "in a twinkling" or, more often, "in the twinkling of an eye" — meaning very fast, in a moment, before you can do anything about it. A twinkling is the tiny time it takes for something to flash, or for an eye to blink. So it is a way of measuring time by using something that takes almost none.

Use it when a change is sudden and complete: "The money was gone in a twinkling." "In the twinkling of an eye the street was empty." It nearly always sits after "in", and it is not something you count — you do not say "two twinklings".

You should know how the phrase feels. It is old and a little literary. "In the twinkling of an eye" comes into everyday English from the Bible, where it describes how the dead will be changed at the last trumpet, and that grand, sudden feeling still clings to it. A modern speaker saying it in an ordinary conversation is being slightly playful or old-fashioned; the plain words are "in a second", "in no time", "in a flash". Recognise it in books, in speeches and in older writing. Use it yourself only when you want that touch of the storyteller.

The same word also works as an ordinary -ing form of the verb twinkle — "the twinkling lights of the harbour" — but that is a different job, and this entry is the time one.