Millisecond/ˈmɪlisekənd/ Definition 1 of 2Pro Tip 1/3Common Expressions Used in everyday language to express speed or a very short time. I'll be back in a millisecond. Pro Tip 2/3Hyperbole 'Millisecond' can be used hyperbolically to mean 'very fast' or 'almost instantly'. My heart skipped a beat for a millisecond when I saw the results. Pro Tip 3/3Not Literal Often 'millisecond' is not literal but emphasizes a brief moment that felt quick. When our eyes met, it lasted only a millisecond.