What is Ejective-contour click?

Ejective-contour clicks, also called sequential linguo-glottalic consonants, are consonants that transition from a click to an ejective sound, or more precisely, have an audible delay between the front and rear release of the click. All click types have linguo-glottalic variants, which occur as both stops and affricates, and may be voiced. At least a voiceless linguo-glottalic affricate is attested from all Khoisan languages of southern Africa , as well as from the Bantu language Yeyi from the same area, but they are unattested elsewhere.