Gault was an inhabited planet. This was the home of a Federation colony with a sparse population of no more than 20,000 inhabitants. It was widely regarded as a "farmworld". (TNG: "Heart of Glory"; DS9: "Let He Who Is Without Sin...")
In 2346, Sergey and Helena Rozhenko lived on Gault with their son, Nikolai; the following year, their adopted son Worf went to live there. One of the secondary schools on Gault had a soccer team which Worf captained in 2353 at the age of thirteen. Worf headed a ball into the goal and accidentally killed the opposing player named Mikel. (TNG: "Homeward"; DS9: "Let He Who Is Without Sin...")
This planet was only mentioned in dialogue.
"GALT" was the pronunciation for this planet's name from the script pronunciation guide for "Let He Who Is Without Sin".