The sacking of Sligh, 28, who hails from Greenville, S.C., winnowed the number of "Idol" wannabes to nine. The winner will be chosen in May.
"I think it's bye-bye, curly," predicted Simon Cowell, before the results were announced.
Cowell said on Tuesday's program that Sligh's rendition of the Police classic "Every Little Thing She Does Is Magic" was a "mess."
Haley Scarnato and Phil Stacey had the next-lowest vote tallies in the phone balloting, which drew more than 30 million calls and text messages.
Stacey, 29, of Jacksonville, Fla., managed to get on Cowell's good side after his solid cover of "Every Breath You Take."
"This may surprise you, Phil, but I actually thought that was very good," Cowell said Tuesday.
The acerbic judge was not as nice to Scarnato, deriding the 24-year-old Texas girl's take on "True Colors" as safe and forgettable.
(Question: Will Sanjaya Malakar, who is undoubtedly a national sensation, stick around until the finale? Could happen, as long as the "Idol" oddball keeps stoking watercooler discussion.)
Wednesday's elimination show also featured a get-up-and-dance performance byand rapper Akon, who performed Stefani's hit single "The Sweet Escape."
In its sixth season, "American Idol" continues to rule the ratings. It has attracted 26 million to 37 million viewers per telecast this season.