in forma pauperis

from The Century Dictionary.

• noun In the character of a pauper. Courts of equity having discretionary power to award or refuse costs adopted the practice of granting leave to sue, without liability to costs in case of unsuccess, to suitors showing a good cause of action, and making oath to poverty, the privilege being confined to those not having above £5 or $20. The power to grant such leave is now generally extended by statute to common-law courts, and in some jurisdictions the limit has been increased.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adverb In the form of a pauper.
• noun law A request to have a court waive filing fees in a civil action because the plaintiff is a pauper.