Hel*lo" (?), interj. & n. See Halloo.

• A greeting (salutation) said when meeting someone or acknowledging someone's arrival or presence.
        Hello, how are you today?
  
• A greeting used when answering the telephone.
        Hello?
  
• A call for responses if it is not clear if anyone is present or if a telephone conversation may have been disconnected.
        Hello? Is anyone there?
  
• (colloquial) Used sarcastically to imply that the person addressed or referred to has done something the speaker or writer considers to be foolish.
        You just tried to start your car with your cell phone. Hello?
  
• An expression of puzzlement.
        Hello? What's going on here.
  
• (with specific pronunciation) Used (usually by male) to signify the arrival of an attractive female.
        Hello. (length drawn out — 'Heeellloooo').
  
• The greeting hello is among the most generic and neutral in use. It may be heard in nearly all social situations and in nearly all walks of life, and is unlikely to cause offense.
  
• In some languages translated word of hello is just not mere greeting but also accompanies some meaning or well wishing to opposite person. For example, the Urdu greeting Assalam-u-alaikum means May peace be upon you.
  
• (AU) (informal) g'day
  
• (US) (informal) hallo, hey, hi, howdy
  
• (slang) wassup, what's up, yo, sup