Vitrophyre
A vitrophyre is a porphyritic volcanic rock in which phenocrysts are embedded in a glassy matrix. Vitrophyres are contrasted from typical porphyritic rocks in that the latter has both crystalline phenocrysts and a crystalline matrix, whereas the former has a distinctly glassy matrix.
Vitrophyres can be alternatively described as rocks having vitrophyric texture. This texture results from the rapid quenching of a lava where phenocrysts had started to form prior to eruption.