from The American Heritage® Dictionary of the English Language, 4th Edition
- interj. Used to greet someone, answer the telephone, or express surprise.
- n. A calling or greeting of "hello.”
- intransitive v. To call "hello.”
from Wiktionary, Creative Commons Attribution/Share-Alike License
- interj. A greeting (salutation) said when meeting someone or acknowledging someone’s arrival or presence.
- interj. A greeting used when answering the telephone.
- interj. A call for response if it is not clear if anyone is present or listening, or if a telephone conversation may have been disconnected.
- interj. Used sarcastically to imply that the person addressed or referred to has done something the speaker or writer considers to be foolish.
- interj. An expression of puzzlement or discovery.
- n. "Hello!" or an equivalent greeting.
from the GNU version of the Collaborative International Dictionary of English
- interj. An exclamation used as a greeting, to call attention, as an exclamation of surprise, or to encourage one. This variant of halloo and holloo has become the dominant form. In the United States, it is the most common greeting used in answering a telephone.
from The Century Dictionary and Cyclopedia
- An exclamation designed to attract the attention of a person at a distance; also, a mere greeting between persons meeting.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. an expression of greeting
Alteration of hallo, alteration of obsolete holla, stop!, perhaps from Old French hola : ho, ho! + la, there (from Latin illāc, that way).(American Heritage® Dictionary of the English Language, Fourth Edition)
Hello (first attested in 1846) from hallo (attested 1840), from holla, hollo (attested 1588). This variant of hallo is often credited to Thomas Edison as a coinage for telephone use, but its appearance in print predates the invention of the telephone by several decades. (Wiktionary)