[ame="http://http://www.youtube.com/watch?v=WMPM1q_Uyxc"]http://http://www.youtube.com/watch?v=WMPM1q_Uyxc[/ame]
Rythm in boxing is not that different from rythm in dancing. It's kind of hard to explain, but picture someone who moves kind of herky-jerky when they shadowbox or spar (like most noobs). Then look at a more experienced boxer who floats effortlessly - even though they are moving fast, they look like they're dancing cuz their upper body and hands and feet are seemingly syncronized. When they duck or slip, or rotate, they aren't just reacting to punches, they are anticipating them beforehand. Similarly, someone who's learning a dance for the first time, lacks the smoothness and effortlessness of someone more experienced. That more experienced dancer can not only match the rythm of the song, but add their own little ad-libs without losing the timing. So in boxing, rythm helps make your movements quicker & more fluid and make your punches more in line with your steps, therefore making you more efficient, spending less energy while being quicker and maintaining better position. If you were hypothetically to step and punch and duck & slip to the beat of a song, that's an example of rythm. Realistically, you'd never want to be THAT predictable, but that's a very basic example. Boxers that have rythm leverage this basic idea and change up the speeds and frequencies very quickly. I don't think there's an easy way to describe having rythm in boxing, but I hope this helped.
:deal ill tell you something though, maybe its just me but once i completely analyze and know what the other person is doing you sort of get into this zone of complete confidence and you attack like it's completely natural also sort of like you're dancing.