bright line
n.— «“Bright lines,” as in “bright-line rule,” meaning a clear, unambiguous standard, are in demand in other contexts as well.» —“Bright lines and the search for certainty” by Ruth Walker Christian Science Monitor (Boston, Mass.) Dec. 15, 2005. (source: Double-Tongued Dictionary)
Further reading
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...
Cat hair may be something you brush off, but cat hair is also a slang term that means “money.” In the same way, cat beer isn’t alcoholic — some people use cat beer as a joking term for “milk.” And imagine walking on a...