• AQUEOUS (adjective). The adjective AQUEOUS has 2 senses: 1. similar to or containing or dissolved in water. 2. produced by the action of water. Familiarity information: AQUEOUS used as an adjective is rare. AQUEOUS (adjective). The adjective AQUEOUS has 2 senses: 1. similar to or containing or dissolved in water. 2. produced by the action of water. Familiarity information: AQUEOUS used as an adjective is rare.