unread

Short definition from Wiktionary

Adjective

1. 1
   Not having been read.
2. 2
   Not having read; uneducated.

Verb

1. 1
   To undo the process of reading.
2. 2
   To flag (a previously read e-mail or similar message) as not having been read.

Noun

1. 1
   An unread email or instant message.