fastness
noun uk/ˈfɑːst.nəs/ us/ˈfæst.nəs/
(FIXED)
[ U ]牢固性；不褪色性
how fast (= fixed) something is
Test clothes for colour fastness before washing. 清洗前要检查衣物是否褪色。
(SAFE PLACE)
[ C ] literary要塞，堡垒
a safe place, such as a fortress
a mountain fastness 山间要塞