1.Dancing, only HARDCORE.
2.The kind of dancing you see the weird suburban kids from your school that always smell like BO and cloves doing. A subtle artform that manages to look uncoordinated, supremely lame and immensely queer, all at the same time. Popular hardcore 'dance moves' include the 'I'm flailing my arms about like a frightened kid in special ED!', The 'I'm piling myself on top of you but it's not gay because we're dancing and it's hardcore!' The 'When you can't dance, just roundhouse kick at random because it totally worked for the Spice Girls!' and the 'I'm going to be a virgin for a long time'.
3.The source of some of the funniest definitions I've come across on this site.

Acrobatic, kung-fu style dancing to hardcore music such as Blood for Blood, Earth Crisis and 25 ta Life, but has leaked into metallic hardcore, nu-metal/metal and emo scenes over time. Generally reserved for macho dudes, dudes trying to get into a fight, or dudes trying to impress other dudes with their "skills". Types of hardcore dancing includes spin kicks, "picking up change", pile-ons, as well as other physically challenging (and often hilarious to watch) martial-arts style moves. Can be enjoyed by straightedge and non-straightedge dudes alike, yet girls seem to shy away from displaying such behaviors too often.

Originally a traditional war dance done during breakdowns at hardcore shows. Unfortunately this once sacred dance can be seen at emo and metal shows. The fine dance has been leaked into the mainstream and everyone and their mother thinks they can dance now. Very few people can actually dance well now (see Philadephia).

A stupid form of "dancing" done by emo kids at "hardcore" shows cause they're too sissy to actually mosh. The saddest part about it is that they actually think they're cool when they do it, when in fact it's the complete opposite.

A type of dance performed at non-punk hardcore shows. It involves violent FLAILING of the arms and legs with no reguard to your friends around you. It was developed to blatantly show you do not belong in the punk subculture and have no roots to it. It is used by kids who are too stupid to learn to skank or circle pit properly. Its not cool in any way and a year later when you "grow out" of whatever fad is big in hardcore, you realize how much of an ass you looked like the whole time. The typical person hardcore dancing is one of the older members of the scene who played in a band but they left the fad and he remains. He doesn't have anything going for him and really only dances to try and impress the young and impressionable girls at the shows. A grade A loser fashion Dance.

hardcore dancing is done at hardcore or metalcore shows. A very fast and energetic type of dance, that has many varients.
2-step-when you flail your arms and put one foot in front of the other, usually done not moving
windmill-when you plant your feet and swing your arms fast during a breakdown
spin kick- very fast spin of the body where you shoot your leg out after the first 180
some people on the outside of the pit like to lean in and do one armed windmills/

Hardcore dancing is dancing for people who don't have the balls to mosh.