"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."