A separation technique in which the mobile phase is a gas. Gas chromatography is always carried out in a column.
Sources:
Orange Book, 2nd ed., p. 93 (https://media.iupac.org/publications/analytical_compendium/)
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2191 (https://doi.org/10.1351/pac199062112167)
PAC, 1993, 65, 819. 'Nomenclature for chromatography (IUPAC Recommendations 1993)' on page 825 (https://doi.org/10.1351/pac199365040819)