Literary or formal word for an extremely short time. Often used with に as an adverbial phrase meaning 'in a flash'.
It happened in a flash.
It vanished in an instant.
瞬間 is the common, everyday word for 'moment' or 'instant'. 一刹那 is more literary and emphasizes extreme brevity.
Standard kanji spelling.
Irregular kanji usage. Not recommended for learners.
From Buddhist terminology, where 一刹那 refers to the shortest unit of time (one thought-moment). The kanji 刹那 is a transliteration of Sanskrit kṣaṇa.