Abracadabra is considered to be the most universally adopted phrase that is pronounced in other languages without translation. One hypothesis about the source of the word is Aramaic: Avrah KaDabra which means I will create as I speak. Due to its universal acceptance, it has been speculated by Bible-believers that the word predates the confusion of languages granted at the Tower of Babel in biblical times.

It is now commonly used as an incantation by magicians. In ancient times, however, the word was taken much more seriously as an incantation to be used as a cure against fevers and inflammations. The first known mention was in De Medicina Praecepta by Serenus Sammonicus, physician to the Roman emperor Caracalla, who prescribed that the sufferer from the disease wear an amulet containing the word written in the form of an inverted cone:

A B R A C A D A B R A
A B R A C A D A B R
A B R A C A D A B
A B R A C A D A
A B R A C A D
A B R A C A
A B R A C
A B R A
A B R
A B
A

This, he explained, diminishes the hold of the spirit of the disease over the patient. Other Roman emperors, including Geta and Alexander Severus, were followers of the medical teachings of Serenus Sammonicus and are likely to have used the incantation as well.

There is also the view that Abracadabra derives from the Hebrew, ha-brachah, meaning "the blessing" (used in this sense as a euphemism for "the curse") and dabra, an Aramaic form of the Hebrew word dever, meaning "pestilence." They point to a similar kabbalistic cure for blindness, in which the name of Shabriri, the demon of blindness, is similarly diminished. Other scholars are skeptical of this origin and claim that the idea of diminishing the power of demons was common throughout the ancient world, and that Abracadabra was simply the name of one such demon.

Some point to the Hebrew words ab ("father"), ben ("son"), and ruach hacadosch ("holy spirit").

Some have argued that the term may come from the Arabic Abra Kadabra, meaning 'let the things be destroyed' or from the Aramaic abhadda kedhabhra, meaning 'disappear like this word'. Rather than being used as a curse, the Aramaic phrase is believed to have been used as a means of treating illness.

It has also been claimed that the word comes Abraxas, a Gnostic word for God (the source of 365 emanations, apparently the Greek letters for Abraxas add up to 365 when deciphered according to numerological methods).

See also: Hocus Pocus, presto and Avada Kedavra (a Harry Potter reference).
Read the "Holy Books of the Golden Dawn"
by Thanatos February 2, 2005
An exclaimation of joy, fear, or nervousness. As made popular by the Dave Chapelle movie "Half Baked"
"Abra Kadabra? All the Cool Kids say it. Abracadabra!"
"Yo Abracadabra B"
by nizzlenuk August 3, 2006
Title track of the 1982 album that ruined Steve Miller's career.
<MasterSean2k> Currently playing: Steve Miller Band - Abracadabra (0:08/5:06)
<seiken> :(
by MasterSean2k December 11, 2004
A magical word that helps someone pull off a miracle.
He looked into the empty hat, said the magic word "Abracadabra!" and pulled a rabbit out of the hat!
by MoonSphynx August 12, 2004
The term used in Half Baked to inform the baked cops in the van when the drug deal was acomplished.
"Abracadabra B" "Yo i said Abracadabra B"
by In memory of T-Nugget February 26, 2006
The act of removing a wedgie from one's backside that is so far up, that one's hand disappears then reappears after said wedgie is removed.
Dude you had a killer Abracadabra
I thought you had lost your hand!
by dude December 4, 2003