sealant

noun

1. a substance used for sealing, as sealing wax or adhesives.
2. any of various liquids, paints, chemicals, or soft substances that may be applied to a surface or circulated through a system of pipes or the like, drying to form a hard, watertight coating.
3. Dentistry. any of several transparent synthetic resins applied to the chewing surfaces of molars and premolars in young children and teenagers as a preventive measure against tooth decay in the occlusal pits and fissures.

noun

1. any substance, such as wax, used for sealing documents, bottles, etc
2. any of a number of substances used for stopping leaks, waterproofing wood, etc

n.1945, from seal (v.) + -ant.