T-glottalization

T-glottalisation is a process that occurs for many English speakers, that causes the phoneme /t/ to be pronounced as the glottal stop in certain positions. This is an instance of the more general phonetic phenomenon (also found in other, unrelated languages throughout the world) called glottalisation. Apparently, glottal reinforcement, which is quite common in English, is a stage preceding full replacement of the stop, and indeed, reinforcement and replacement can be in free variation.