A lisp is a speech impediment, historically also known as sigmatism. Stereotypically, people with a lisp are unable to pronounce sibilants, and replace them with interdentals, though there are actually several kinds of lisp. "Interdental" lisping is produced when the tip of the tongue protrudes between the front teeth and "dentalised" lisping is produced when the tip of the tongue just touches the front teeth.
The "lateral" lisp, where the 's' and 'z' sounds are produced with air escaping over the sides of the tongue, is also called 'slushy ess' or a 'slushy lisp' due to the wet, spitty sound.
Finally there is the "palatal lisp" where the speaker attempts to make the sounds with the tongue in contact with the palate.
One of the prevailing stereotypes about homosexuals, particularly males, is that they are perceived to talk in an unusually high-pitched voice with a lisp.
The interdental lisp is actually standard in the Turkmen language.
Notable people that had or have lisps include:
Alcibiades
Charlie Angus
Drew Barrymore
Jello Biafra
Campbell Brown
David Carradine
Nat King Cole (in his early career).
Dolores Costello
Alan Davies
Dan Dierdorf
Ric Flair
Rudy Giuliani
Rich Hall
Jimi Hendrix
Keith Hernandez
Thomas Jefferson
(who preferred writing to public speaking partly because of this)
Kristin Kreuk
Josh Lewin
Barry Manilow
Mike Mayock
Jack Norman
Susan Olsen
Josh Peck
Ellen Pompeo
Rhymefest
Romario
Sara Rue
Virgil "Dusty Rhodes" Runnels, Jr.
Leon Schlesinger
Chuck Schuldiner
Shannon Sharpe
Russell Simmons
Vincent Simone
Mike Tyson
Barbara Walters
Morgan Webb
Criss Angel
Zach Revinsky
John Adams also had a lisp in his later years, but this was because he refused to wear dentures. Moses is described as having "slow speech and a slow tongue" (Exodus 4:10), which is traditionally interpreted as a lisp, though others have believed it was a stutter or merely hesitancy. Winston Churchill had a slight lisp, which is often incorrectly said to have been a stutter. Bryan Murray, head coach of the Ottawa Senators has a strong lisp.