I just came across a wonderful, linguistically descriptive definition for the word "drawl" in Webster's Third New International Dictionary, Unabridged. Since I have posted many times about dialects, and a Southern drawl is a regional dialect, I thought I would share:
"to speak slowly esp. as a matter of habit with vowels greatly prolonged so that vowels monophthongal in other styles of speech are often diphthongized (as in bin, web, bad, knob, talk, good)."
If you are unfamiliar with the words "monophthong" and "diphthong," they are defined as follows by thefreedictionary.com:
1. A single vowel articulated without change in quality throughout the course of a syllable, as the vowel of English bed.
2. Two written vowels representing a single sound, as oa in boat.
A complex speech sound or glide that begins with one vowel and gradually changes to another vowel within the same syllable, as (oi) in boil or (1) in fine.