Question

ɫ English wool, pill, until, well, ball. "Dark" l. English l and ll becomes "dark" automatically when it is in syllable-final position (or non-syllable initial position). Compared to the "clear" l, the back of the tongue is raised. The tongue may or may not touch the alveolar ridge.

Accepted Answer

Velarized Alveolar Lateral Approximant http://en.wikipedia.org/wiki/Velarized_alveolar_lateral_approximant

Symbol	ɫ
Name	Velarized Alveolar Lateral Approximant
Notes	English wool, pill, until, well, ball. "Dark" l. English l and ll becomes "dark" automatically when it is in syllable-final position (or non-syllable initial position). Compared to the "clear" l, the back of the tongue is raised. The tongue may or may not touch the alveolar ridge.
Ref	http://en.wikipedia.org/wiki/Velarized_alveolar_lateral_approximant

L Ll Alveolar English Dark Tongue ɫ Velarized