Linear A

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An undeciphered writing system used in Crete from the 18th to the 15th century BC.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• proper noun a syllabary used to write the as-yet-undeciphered Minoan language, and an apparent predecessor to other scripts, such as Linear B

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an undeciphered writing system used in Crete in the 17th century B.C.