"Word" ...defined:

1. Word
1) well said
2)said in a agreement
3) can be used as a greeting, hey whats up
1..and 2...Yo u goin to that rocks tanite....word
3) word up

2. word
A versatile declaration, originating (more or less) in hip-hop culture.

"Word" has no single meaning, but is used to convey a casual sense of affirmation, acknowledgement, agreement, or to indicate that something has impressed you favorably.

Its usage among young blacks has been parodied ad nauseam among clueless suburban whites.
"Come on, man, we're going to the store."
"Word."

3. Word
Affirmative.
Can also be used as a question, meaning "really?"
"Man, this sucks."
"Word."

also

"I just got a new car!"
"Word?"

4. word
to concur
I'd like to hit Monica from the backside, yo!!
Word!!

5. Word
"I agree." can be used to express agreement and approval in several ways.
1. a: "Man, that song rocks."
b: "word!"

2. a: "I'm not gonna take crap from him anymore."
b: "Word!"

6. word
I concur, my fellow African American friends.
"Man, she's got some fine titties!"
"Word."

7. Word
Can be used in place of "really?" or "you fa-serious?"
person #1: Yo Shawty, the po-po's just took Lil D up to da cell!
person #2: WORD?

8. word
A linguistic data packet.

Also a multiple-byte unit of information in computer science/engineering.
These are all words.

9. Word
adv.

Used to express an agreement or affirmation.
Carl: Yo, you want some of these Funyuns?
Phil: Word.

10. word
agreed or a way of saying you understand where the person is coming from
word to that, my brother