sealant

a substance used for sealing, seal, as sealing wax or adhesives.

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.

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.