fictitious defendants

Definition from Nolo’s Plain-English Law Dictionary

When a party suing (plaintiff) is not sure whether there are unknown persons involved in the suit, they are given fictitious names, usually designated Doe I, Doe II, and so forth, with an allegation in the complaint that if and when the true names are discovered they will be inserted in the complaint by amendment. Fictitious defendants are not permitted in federal cases.

Definition provided by Nolo’s Plain-English Law Dictionary.