noun
softening water; loosening water
Specifically refers to the small packet of water included with some packaged noodles (like instant yakisoba) that is added to help separate and soften the noodles before cooking or eating. The literal meaning is 'loosening water'.
See also: 解す (ほぐす)
カップ焼きそばのふたを開けて、ほぐし水を入れてください。
Open the lid of the cup yakisoba and add the softening water.
ほぐし水を入れたら、よく混ぜて麺をほぐしてください。
After adding the softening water, mix well to loosen the noodles.