Here is the definition of (Utterance)in the glossary of this site. In the last part, shouldn`t we change the place of (possible)? so that, it would be:...the longest uninterrupted possible speech.
An Utterance is a complete unit of speech (what one speaker says before the next starts), ranging from a single word to the longest uninterrupted speech possible.
Thanks in advance,
Fine either way to me.