Burp
A burp or belch was the expulsion of gas from one's stomach. 

In 2287, a drunk General Korrd greeted Romulan ambassador Caithlin Dar with a rather loud burp when she arrived at Paradise City on Nimbus III. ()

In 2370, suffering from the early stages of Barclay's Protomorphosis Syndrome, a voracious Worf burped while sharing a table in Ten Forward with Deanna Troi, who promptly excused him. ()

In 2371, Bo'rak belched drunkenly within close proximity of Odo. ()

In 2375, Quark imagined Sto-vo-kor as "hoards of rampaging Klingons fighting and singing, sweating and belching" when Julian Bashir expressed his desire to help Jadzia Dax enter the Klingon afterlife. Bashir quipped that it sounded like Quark's on a Saturday night, to which the Ferengi countered with Bashir would wish to spend eternity in Quark's. ()

External link 
 
Medical conditions
Physiology