What does "thou dost snore distinctly. There's meaning in thy snores." mean in the Tempest?

In simple words, he is saying that the other man snores in a particular way (different from the way other people snore/sound) - - maybe with certain sounds, presumably. To say that there's meaning in the snores suggests that he can (in his mind, anyway) detect a sort of language or communication.

Explanation:

'Distinctly' indicates in a way that is readily and clearly distinguishable by the senses - - something that is very noticeable or apparent.