I don't know how to explain them, so I'll just give links to examples.

From about 4:40 to the end in this song

4:26 to about 4:43

6:17 to 6:35

Is there any specific name for these, or are they just badass riffs that sound really similar? Also, sorry if this is a stupid question :S
Quote by blacksurgeband
I thought breakdowns were supposed to be a lot slower.

not always, they normally are just a short spot of heavy, deep sounding riffs