It is a court order, usually served by ;aw enforcement that requires immediate requiring that you immediately turn over the child.
If things have gotten to that point, you need a lawyer. Immediately.
IF you were served with a Writ of Habeas Corpus, it had a court date on it. If you did not appear in court, then the court ruled in favor of the other party and the Habeas is "disposed." Or if neither party showed up, the court just dismissed the Habeas and it is "disposed." You need to contact the clerk of court to find out what happened or hire an attorney to find out what the situation is.