Greek 
(grēk)
(grēk)n.
1.
a. The Indo-European language of the Greeks.
b. Greek language and literature from the middle of the eighth century BC to the end of the third century AD, especially the Attic Greek of the fifth and fourth centuries BC.
2.
a. A native or inhabitant of Greece.
b. A person of Greek ancestry.
3. Informal A member of a fraternity or sorority that has its name composed of Greek letters.
4. Informal Something that is unintelligible: Quantum mechanics is Greek to me.
adj.
Of or relating to Greece or its people, language, or culture.
[Middle English Grek, from Old English Grēcas, the Greeks, from Latin Graecus, Greek, from Greek Graikos, ethnic designation of a Boeotian tribe that settled in Italy.]