Glottal stop is a sharp closer of the glottis. It takes place for instance in the English interjection un-oh or in the American English pronunciation of kitten.
Glottal stop is part of the glottalized stops č’, k’, p’, t’ introduced earlier, but it also occurs after s, š and ȟ.
Listen to the following recording and select what you hear:
Glottal stop is also pronounced between vowels, whenever two vowels occur next to each other. It is, however, pronounced only in slow formal pronunciation. Read more about this in NLD.1 page 695 (2.1.4).