A word often used in place of a period at the end of a sentence, with the voice trialing off.
It suggests that the speaker thinks that more should be said, but there may be nothing to logically follow it.
Heard on David Letterman in a Rupert Gee episode where a lady off the street ended every sentence with ", so ..." "Where are you from?" "I'm from Cleveland." "What are you doing for a good time in New York?" "We're going to shows and walking around, so ..." "Having fun?" "A lot of fun, so ..."