It is often used to describe a specific point in time, for example:
* Istante di gloria: Moment of glory
* Istante di paura: Moment of fear
* Istante di silenzio: Moment of silence
It can also be used in a more figurative sense to describe a fleeting or ephemeral experience:
* Istante di felicità: A fleeting moment of happiness
* Istante di bellezza: A moment of beauty
The translation will depend on the context of the sentence.