Does uttering the word "tahrim" (prohibition) without intention or purpose mean it is null and void, and that the word "haram" is a common expression with no implications, except for the prohibition of one's wife when intended, and otherwise it means nothing?

If the husband intends a real prohibition (تحريم حقيقي) by the word "tahreem" (prohibition), then whatever he prohibits incurs an expiation for an oath (kaffarat yameen). As for prohibiting his wife, if the husband intends by the word "tahreem": Dhihar, then it is Dhihar; or Ila', then it is Ila'; or divorce, then it is divorce. If he does not intend anything, then he must pay an expiation for an oath. However, if he did not intend prohibition at all, then nothing is incumbent upon him.