Use the verb rhapsodize to refer to speaking with extreme enthusiasm — and often at great length, like that friend who tends to rhapsodize about her favorite movie for twenty minutes straight.
To correctly pronounce rhapsodize, say "RAP-so-dies." A rhapsody is a conversation or speech that is elaborate and very emotional, so to rhapsodize is to speak that way. Someone with a tendency to rhapsodize gets carried away with the emotion of the topic. That's why when you rhapsodize you don't always notice that listeners stop listening if they don't share the same passion.