: a native or inhabitant of ancient or modern Greece
b
: a person of Greek descent
2
a
: the language used by the Greeks from prehistoric times to the present constituting a branch of Indo-European see Indo-European Languages Table
b
: ancient Greek as used from the time of the earliest records to the end of the second century a.d. see Indo-European Languages Table
c
often not capitalized[translation of Latin Graecum (in the medieval phrase Graecum est; non potest legi It is Greek; it cannot be read)]: something unintelligible
it's Greek to me
3
: a member of a Greek-letter fraternity or sorority