The phrase "sit one butt" is spelled as /sɪt wʌn bʌt/. The word "sit" is spelled with the "s" and "t" representing the /s/ and /t/ sounds, respectively. "One" is spelled with the "o" and "e" representing the /w/ and /n/ sounds, respectively. "Butt" is spelled with the "b" and "t" representing the /b/ and /t/ sounds, respectively. This phrase is used colloquially to mean "sit down" and is often heard in casual conversation.