An adjective describing tedium, bordom, or undescribable hell.
It stems from the common adjective ending of "-ing" and is simply repeated but said differently. A dragged accent is spoken on the first "ing" rather than the second. Normally when spoken, there is a pause prior to the word. When written, an elipses comes before it. Use it cautiously.
What a great term paper! It's just so...ing-ing!