A glottal stop could be defined as a catch in the back of the throat using the glottis. Henceforth I represent the glottal stop as ('). I was told by some linguist that the word "apple" actually begins with a consonant which is the glottal stop. Maybe so. In the Cockney variety of British English the word "bottle" is pronounced "bo'l". The "t" is glottalized. Although Cockney may declining, I would guess that it can still be heard in some parts of London. I have noticed that some speakers of American English pronounce the word "beyond" as "be'ond", glottalizing the "y". I wonder why they do that. What could be wrong with pronouncing the "y"? Maybe you have never noticed this glottalized pronunciation of that word, but keep listening. Or maybe you pronounce the word that way.

That would be John McWhorter, most likely. He didn't quite say that apple began with a glottal stop, but that a glottal stop epenthesized when a speaker said "a apple."

Cockney may be on the decline, but Estuary incorporates many of its features--including glottalisation of non-initial /t/--and it's very much on the march. You'll hear more glottal stops on the British airways these days than ever before.

I'm American (fairly neutral Californian accent) and I usually pronounce a glottal stop in words like "button", "mitten", "smitten", etc. I definitely pronounced the "y" in "beyond" though. Don't think I've ever heard it pronounced as a glottal stop, but I'm sure it is somewhere. It's interesting that it would be pronounced that way. You'd think palatalization would be an easier transition than a glottal stop.

Not an expert here, and probably this is irrelevant, but glottal stops in English seem to occur for two reasons. One, epenthesis, like somebody said: we feel a need to separate vowels and sometimes we take it farther than the intended purpose. Two, /t/ is often unreleased in syllable-final position, and unreleased /t/ can in turn be realized as a glottal stop in some (or maybe all) dialects of English.

The Barbadian accent (from the Caribbean) has a lot of glottal stops.

Here is an example from You Tube: http://www.youtube.com/watch?v=mDtt7KWwlqw

Barbados probably has the largest number of local white Caribbean people, and maybe their ancestors were Cockney speakers or something?

Here are some white Bajans (as Barbadians are called): http://www.youtube.com/watch?v=D5dRT9yU8mc

Scratch that. Canadians apparently release every single final /t/, so definitely not all.

I personally use glo'al stops all the time for /t/ in non-final positions. But less so than a true Cockney.

(Incidentally, the name "Cockney" comes from the words "cockerel" and "eyen" (meaning 'egg'), and as many of the other dialects and accents around Britain found the Cockney accent a mite strange, it was called "Cockney", or a contraction of "Cockerel's eyen". Of course, an egg from a cockerel is not a natural thing!! Hence the name.)

Sometimes it is difficult to distinguish between a "true" glottal stop, and one that is simply an accent or natural pause between sounds. I've always thought of the glottal stop as a much more "forced" or deliberate sound. For instance, I've heard some people put a pause in words like "trouble" -- but its just their manner of speaking, not an element of the word.