You may experience people doing this intentionally (to some extent) in law, politics, religion, or many different areas where they speak vaguely so that they are correct in at least one interpretation of their words. What you think they are meaning may not be the one way in which they are actually correct.
Someone also may do this unintentionally where they use words with more than one meaning or they just overuse general nouns / personal pronouns (she went to that place to get some stuff). They may say "she went to the store" when you ask where someone is, but they might mean a different individual than the one you were asking about.
Someone may speak with an assumed (but not explicitly defined) context.
Statistics that are misleading due to no explanation of the data presented, like "4/5 dentists suggest X toothpaste" but it isn't mentioned how many dentists were asked, where these dentist offices are, if they were paid for their answers, etc.