adj

• (obsolete) Unwary; unready (especially in the phrase take (someone) tardy).
  "Be not ta’en tardy by unwise delay."
• (obsolete) Criminal; guilty.
  "And the Franks served the Men much the same ſauce when they found them tardy, and made them run their Heats through the Streets"

noun

• (US) A piece of paper given to students who are late to class.
  "The teacher gave her a tardy because she did not come into the classroom until after the bell."
• (US) An instance of a student's being marked as tardy by a teacher on the teacher's attendance sheet.

verb

• (obsolete, transitive) To make tardy.
  "the good mind of Camillo tardied My swift command"
• (rare, intransitive) To dawdle.
  "Sitting there on the rock behind the school, I heard nothing but the occasional raised voice of some youngster tardying on his way home, and the joints in the schoolhouse squeaking from the frost."