Google have switched the content provides to its Dictionary product. "Earlier, Google used Collins COBUILD Advanced Learner's English Dictionary but now they have switched and now using Oxford Pocket Dictionary of Current English. So, what's the difference between the two? Well, here are two words with different explanations:
Collins: "If you call someone a swot, you disapprove of the fact that they study extremely hard and are not interested in other things."
Oxford: "A person who studies hard, esp. one regarded as spending too much time studying."
Compare other words yourself between Collins and Oxford.