unprepared

From un- +‎ prepared.

unprepared (comparative more unprepared, superlative most unprepared)

1. Not prepared; caught by surprise.

   The castle was unprepared for the assault.

unprepared (plural unprepareds)

1. A black mark given to a pupil who arrives at a lesson without the necessary items or preparation.
   • 1983, Ronald B. Lansing, Skylarks and lecterns: a law school charter, page 116:

     "He's got another rule: Whenever he gets three unprepareds in a row, he leaves the classroom."