Extremely fast, aggressive and insane hardcore dance music usually exceeding 200 BPM with a big phat kick drum. See also gabber which is wrongly seen in USA as some kinda freaky screamo trash metal when in fact it is the same thing i.e. Hardcore Tekno.
Also dutch for friend. A gabbahead is someone who likes hardcore tekno and who usually has a shaved head (see below)
Noun - Unspecific body part that will be in immense pain, once punched (Markiplier fans use to threaten someone who annoys them).
You: Creepers from minecraft really... BLOW my mind!
Friend: If you tell one more bad joke, your Gabba will be in so much pain, you won't even be able to breathe...
Derived from the genre of music, that quite frankly can only be described as noise terror, 'gabba' conveys how something is way too intense or over the top in a negative respect.