"Ya’ni" literally means, "I mean to say,..." It is commonly used as a filler, like the English "you know," a poor substitute for articulate speech. Some people pepper all their sentences with "ya’ni," in which case the listener simply filters it out, just as we filter out "uh...uh" or "um."

In the context you describe, the answer given to the question about health or work is "mediocre," "passing," "not so hot," or as Bushra2u said, "so so." The word "ya’ni" is used here as though the speaker is going to elaborate some more, but then fails to do so on the pretext that "ya’ni" sums it up.

Where I come from, it is not uncommon to hear people, especially women, say "ya’nu" instead.

The use of "ya’ni" often becomes a habit that is hard to break. I know some Arabic-speaking friends who use it even when they speak English. Incidentally, I have heard the same expression used in Turkish conversations as well. I am not sure if it is used in the same manner in Turkish as in Arabic.

So, how was the weather in Amman? Ya’ni....

Fuad