Verba fortius accipiuntur contra proferentem

n. (Latin) fundamental law of construction according to which if words of an agreement/contract are vague (and have two possible meanings in an equal manner) they should be interpreted against the person who wrote the words and not against the other party (Law)

Latin: a principle of construction whereby if words of a contract are ambiguous, of two equally possible meanings, they should be interpreted against the author, drafter or writer of the contract and not against the other party. - (read more on Verba fortius accipiuntur contra proferentem)