2) Acknowledgement of someone who has greeted you, or a greeting in itself.
3) A state of mind, in which one is relaxed.
4) A neural vowel sound used in the dictionary, depicted as a lowercase letter 'e', rotated 180 degrees counter-clockwise.
Slang originated from Hashmeer of Group X, who used the phrase "Shiggity shiggity schwa." Eventually, Jager, of The Hoodlums in Upstate New York, began to use Schwa inan every day context.
2) "Hey dude."
3) "How do you feel?"
Marty: that noise, it's over there in the corner.
Finn: you're crazy
Friend 2 (a schwa): "Heh heh heh."