Daniels:

abugida a type of writing system whose basic characters denote
consonants followed by a particular vowel, and in which diacritics
denote the other vowels

The Unicode Standard:

Abugida. A special type of writing system encompassing the many
scripts of South and Southeast Asia that are historically derived
from the ancient Brahmi script. The term abugida is derived from the
North Semitic alphabetic order: alef, bet, gimel, dalet.

Daniels commented:

>The differences: No definition whatsoever; omission of Ethiopic;
>wrong statement of etymology (maybe John was subconsciously ashamed
>of the poorness of the passage, and omitted it Freudianly!)

So, given this, and admitting hand-on-heart that Peter Daniels is
right and that the existing Unicode definition sucks, one might
propose the following revision:

Abugida. A writing system in which consonants are indicated by the
base letters which have an inherent vowel, and in which other vowels
are indicated by additional distinguishing marks of some kind
modifying the base letter. The Ethiopic script is an abugida, as are
the many scripts of South and Southeast Asia that are historically
derived from the ancient Brahmi script. The term "abugida" is derived
from the first four letters of the traditional order of the Ethiopic
script (ALF, BET, GAML, DANT).

Comment is invited.
--
Michael Everson * * Everson Typography * * http://www.evertype.com