When speaking of (alleged) attempts to lie or cover up the truth, someone might say "truth will out," an expression that seems to make no sense: where is the verb?
"Will" can be used as a verb, but it only works in connection with another verb, as in "He wills it to happen." "Out" can also be used as a verb, but it's a transitive verb: "Bob outed Alice as a spy." Neither of these conditions apply in this phrase.
If the word "come" was added in there, we would have "truth will come out," which is both grammatically correct and appears to clearly convey the meaning of the phrase. But it gets used without any verb, which makes the meaning of the phrase a lot less clear.
What exactly does "truth will out" mean, and why is the expression used in such an ungrammatical way?