This article, Water Release: Water Mirror Technique, contains content taken directly from our mother site. All credit of such content is reserved the original authors over at Narutopedia, the original article can be read here: "Water Release: Water Mirror Technique".
The user creates a large, flat, circular pool of water in front of their opponent. Its surface acts like a mirror, perfectly reflecting the attacking targets. By then rotating the 'mirror' 90°, the reflections emerge and materialise from the mirror, where they collide with the mirrored targets. As these reflections use the exact same techniques as the enemy regardless of its type, they counter their respective target's attack completely, while repelling them in the process. However, upon impact, the reflections disperse back into water.
Like many other Water Release techniques before it, Fuyuki has likewise found a way to empower the Water Mirror Technique by combining it with his mastery of water. While the orginal version only summoned a single mirror Fuyuki employs a variation which allows him to rather than create a new mirror use the natural reflective surfaces of clear water instead as a sufficient medium. This reinvention of the Water Mirror Technique allows Fuyuki to reflect most attacks by using his own chakra-infused water as a mirror, like most of Fuyuki's refined water techniques, this also doesn't require a hand seal due to Fuyuki's mastery over the element in question. In combat however, this technique is rather rarely employed due to the sheer amount of chakra it consumes, and how Fuyuki considers it largely impractical other than in certain situations.
水鏡 is a normal Japanese word referring to a reflective surface of water.