"six jia kong wang 六甲空亡",  " big four void四大空亡", "cut road kong wang 截路空亡" are the terminologies used in zi-ping bazi science. 
"kong wang" terminology is also used in the chinese divination such as liu yao prediction六爻預測, and also in the date selection science擇日學. 
In the zi-wei-dou-shu紫微斗數 science, similar terminologies such as "tian kong 天空", "di kong 地空" stars are used. 
In feng shui science, there are "da kong wang 大空亡",  and  "xiao kong wang 小空亡" terminologies used but the definitions between the san he and san yuan are difference.
As per the san yuan xian kong science, when the yin or yang mansion is having its facing degree pointing right at the boundary line between:
- 2 mountains on luopan, the feng shui terminology is named "xiao kong wang" 「小空亡」which direct translation in English would be "little void and gone", carrying the bad and dangerous luck. 
-.2 qua (trigram) on luopan, the feng shui terminology is named " da kong wang" 「大空亡」 which direct translation in English, would be "big void and gone", carrying very bad and dangerous luck. 
Both scenarios would result san yuan xian kong unable to set up the flying star life pan (plate) for the yin or yang mansion due to unable to identify which luopan mountain is used in the formula for calculation and set-up.
The "kong wang" is having the meanings such as, empty, idle, useless, lost, disappear, missing,..... dead. 
As per the classical literature,  both scenarios above in case of the impact to the yang mansion feng shui would happen to be haunted, residents often unable to sleep well and peaceful,  strangle behaviour developed, loosing sense of family and home belonging, frequent accidents occur,  fire, car accidents, involves in lawsuit cases, robbery, business failure, long time illness unrecovery, various bad luck matters encountered.
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