plural of back forty

plural of north forty

(Canada, US, idiomatic, obsolete) A very fast speed. / (Canada, US, slang, obsolete, by extension) The quality of being "fast", i.e. immoral in one's habits.

(set theory) The paradox that supposing the existence of a set of all ordinal numbers leads to a contradiction; construed as meaning that it is not a properly defined set.

Close to the number forty / About forty years old.

Any number close to forty.

By a multiple of forty; by forty times as much or as many.

By a factor of forty.

(UK) Having a value or cost of forty pence.

Alternative form of forty-eightmo