Fart: This is not an accepted medical word for passing gas. Excess gas in the intestinal is medically termed "flatulence." (But what is excess gas is difficult to define since symptom-free individuals have recorded approximately 14 passages of gas per 24 hours!)
The Oxford English Dictionary (OED), in its inimitable way, notes that the word "fart" is "not in decent use." The OED defines the transitive verb form of fart: "To send forth as wind from the anus 1632." The word comes from the Old English "feortan" (meaning "to break wind"). Although the word "fart" is "not in decent use," it was used by the likes of the great English poet Geoffrey Chaucer.