Why doesn’t it qualify as a word? Everyone makes the same sound, with or without the gesture, and everyone know what that sound means - it symbolizes a particular type of occurrence. To me, that’s a word.
If it were merely a sound effect, it would have to more accurately mimic an actual explosion, which it doesn’t.
Well, I’m going to guess that the reason its not actually a word is because the vocal sounds involved in making it aren’t a normal way. You kind of make a gurgling sound… no other word in the english language does that does it?
I would most likely say the way to spell it would be kapow. As that is what the base of it seems to be, and then when you’re making the sound, you kind of drag it out with some scratchy throat noises, while sluring it all together resulting in a:
More accurate how, exactly? The human vocal apparatus can’t make a realistic explosion sound, so we invent approximate sound effects. This shouldn’t be confused with onomatopoeia, which are words.
You might write about a dog barking with “woof woof” or “bow-wow” or somesuch, but when talking to someone, you’re not likely to say those, but to instead approximate the barking sound as best as you can. However, the sound you create would not be composed of phonyms that exist in the English language, so it could never be correctly written down. And if you can’t write it down, it can’t be used as a standard word.
Consider the ubiquitous (in American culture, at least) “wolf wistle”. You know, the one people make when admiring an attractive person. Is that a word? Lots of people make the same exact sound, and they all know what it means. Its a vocalization with understood meaning, but it could hardly be called a word.