are liquids having a closed cup flash point of not more than 60.5°C (141°F), as universally defined by the U.S. Department of Transportation (DOT), the International Civil Air Organization (ICAO), and the International Maritime Organization (IMO). ICAO and IMO expand the definition by including liquids with an open cup flash point of not more than 65.6°C (150°F). DOT’s hazardous material regulations have refinements that apply to domestic transportation only: l) a combustible liquid is defined as a liquid having a closed cup flash point above 60.5°C (141°F) and below 93°C (200°F). 2) a "flammable liquid" with a flash point at or above 38°C (100°F) that does not meet the definition of any other hazard class may be reclassified as a "combustible liquid" for transportation over land; this provision does not apply to shipment by sea or air. 3) Materials classified as "combustible liquids" that are shipped in packages of 119 gallons or less are exempt from the domestic regulations if they are not subject to classification under any other hazard class. 4) Any material in a liquid phase with a flash point at or above 38°C (100°F) that is intentionally heated and transported at or above its flash point is classed as a "flammable liquid" when transported in bulk packaging. Additionally, any material in a liquid phase that is offered for transportation at or above 100°C (212°F)) is classified and regulated as an elevated temperature material.

Also see closed cup, open cup.