What is Capias Pro Fine?

Legal Definition
Capias pro fine are writs or warrants issued after the defendant defaults on an agreement with the court.

The writ is considered outstanding until paid in full. The recipient usually must remain in jail until fees and/or costs have been satisfied by time served or the fees and/or costs have been paid in full.

In many jurisdictions, including Texas, a defendant taken into custody under a capias pro fine is not transported directly to jail, but is taken before the court which issued the capias and required to show cause why the terms of the judgment were not fulfilled. If the defendant cannot demonstrate good cause, then the defendant can be confined until the terms are lawfully discharged.
-- Wikipedia
Legal Definition
Practice, crim. law. The name of a writ which issues against a defendant who has been fined, and who does not discharge it according to the judgment. This writ commands the sheriff to arrest the defendant and commit him to prison, there to remain till he pay the fine, or be otherwise discharged according to law.
-- Bouviers Law Dictionary
Legal Definition
(That you take for the fine or in mercy.) Formerly, if the verdict was for the defendant, the plaintiff was adjudged to be amerced for his false claim ; but, if the verdict was for the plaintiff, then in all actions vi et armis, or where the defendant, in his pleading, had falsely denied his own deed, the judgment contained an award of a capiatur pro fine; and in all other cases the defendant was adjudged to be amerced. The insertion of the misericordia or of the capiatur in the judgment is now unnecessary. Wharton.
-- Black's Law Dictionary
Legal Definition
A writ for the arrest of one who had not paid a fine.
-- Ballentine's Law Dictionary