50-50 may both refer to a specific position in Brazilian Jiu-Jitsu where your legs are entangled in a mirrored fashion with your opponent's such that neither of you has a distinct advantage, or more generally to any position where both of you and your opponent have equal opportunity to attack and defend so that neither side of the position is more desirable than the other, either because your positions are mirrored, or because both sides of the position have substantial inherent advantages.