in forma pauperis

Century Dictionary and Cyclopedia

1. n. 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.

Wiktionary

1. adv. In the form of pauper.
2. n. law A request to have a court waive filing fees in a civil action because the plaintiff is a pauper.