1a sweet or savoury dish made as a smooth, light mass in which the main ingredient is whipped with cream and egg white:sponge topped with chocolate mousse [count noun]:a salmon mousse
2 [in singular] a mass of tiny bubbles that forms on the top of a glass of champagne or sparkling wine:the Brut Réserve possesses a wonderful creamy mousse of small, compact bubbles
3a light, foamy preparation used for styling hair:apply a dollop of volumizing mousse to the roots and work it in towards the ends of your hair [count noun]:experiment with different styling products such as mousses and gels
a cosmetic or other skincare product with a foamy consistency:this rich shower mousse has an uplifting blend of grapefruit, lemon, orange peel and cedarwood oils
4 (also chocolate mousse) a frothy brown emulsion of oil and seawater formed by weathering of an oil slick.
style (hair) using mousse:mousse each section before winding on rollers (as adjective moussed)his blow-dried and moussed hair