Here's two pachycephalosauruses (pachycephalosauri?) taking each other head on: www.dinopark.cz/dinopark-plzen/ke-stazeni/plzen/images/Pachycephalosaurus.jpg :)

It is a dare (or angry invitation) in which one person invites another person to engage in some challenge or conflict without any reservation or hesitation, holding nothing back. In addition to: You want me? Come and get me! Bring it on! Everything you've got! I'm ready! Also: No holds barred! Meaning everything is permitted in this confrontation (there are no rules).

It means like, "Bring it on" or "Come get me" Kind of like a taunt to make someone mad~ (Where do you keep hearing this stuff?)

good