a broader, more technical term for any material (paste, liquid, or tape) that blocks water or air
Synonym discussion
Sense: noun/2
Mastic, caulk, and putty are all pasty materials used to fill gaps, but they differ in use and setting. Mastic is a general term for thick paste sealants that stay slightly flexible after drying; it is often applied around sinks, baths, and window frames to block water. Caulk is the most common everyday word for the same task — you buy a tube of caulk at a hardware store and apply it with a caulking gun. Putty is stiffer and less sticky; it is traditionally used for fixing glass into window frames or filling small holes in wood before painting. Sealant is a broader, more technical term that covers any material (paste, liquid, or tape) that blocks water or air. In everyday home repair, most people say 'caulk' rather than 'mastic' or 'sealant.'
Mastic entered English in the 14th century through Old French mastic, which came from Latin mastichē and ultimately Greek mastikhē. The Greek word is related to mastikhan, meaning 'to grind the teeth,' because the resin was traditionally chewed like gum to freshen the breath. The building-sealant sense developed much later, in the 19th century, when manufacturers began making paste-like fillers that resembled the natural resin in texture.