from the Oxford Dictionary:
1) the holy hill of ancient Jerusalem, Mount Zion.
2) the Jewish people
3) the Jewish homeland as a symbol of Judaism
4) the kingdom of heaven
from the "Encyclopedic Dictionary" of The New American Bible
, Catholic Bible Publishers, 1971-1972 edition:
A hill located in the southeastern part of Jerusalem. It was originally a Jebusite fortification., but it was captured by David and called the city of David. After the building of the temple, the city and the temple were called Zion; thus, Jerusalem came to be known as "the daughter of Zion," and the term "Zion" was applied to all the people of Israel. In the New Testament, Zion served as a type of Messianic Kingdom.
From the prophet Zechariah (9:9-13):
Rejoice heartily, O daughter Zion,
shout for joy, O daughter jerusalem!
See, your king shall come to you;
a just savior is he,
Meek, and riding on an ***,
on a colt, the foal of an ***.
He shall banish the chariot from Ephraim,
and the horse from Jerusalem;
The warrior's bow shall be banished,
and he shall proclaim peace to the nations.
Hi sdominion shall be from sea to sea,
and from the River to the ends of the earth.
As for you, the blood of your covenant with me,
I will bring forth your prisoners from the dungeon.
In the return to the fortress
of the waiting prisoners,
This very day, I will return you
double for your exile.
For I will bend Judah as my bow..........
subsequent note: I didn't type the *** -- the word is in the bible, but CA seems to automatically bleep it.