"Flood opening" is a phrase often used to describe an opening in a structure intended to allow water to flow freely during flooding. However, there are several synonyms that can be used interchangeably with "flood opening." Some of these include "floodgate," "sluice gate," "flood relief valve," "overflow weir," and "drainage channel." While each of these synonyms may describe a slightly different type of opening or structure, they all serve the same essential purpose of preventing damage from floodwaters by providing a means for water to flow safely away from structures and into designated drainage areas.