Overgearing describes a situation where a player's equipment is powerful enough to minimize or outright negate the usual dangers of a fight, especially those relying on pure damage to endanger players. This is usually in reference to newer content essentially obsoleting older content as players find a easier way to acquire equipment that was not intended for a previous fight (which addtionally tends be to re-tuned to be easier). The term is sometimes used pejoratively, describing where the previous content is steamrolled but does not include an improvement of tactics or avoidance, simply that a player cannot be harmed as easily.
A major exception to this are scenarios where the players equipment is essentially meaningless, such as most vehicle fights, or were attacks by enemies have an effect by percentile amounts.