A film or layer of floating matter formed upon the surface of a liquid in a state of fermentation, ebullition, etc.; hence, a film formed upon…

= scum, n. 2b. Obsolete.

A mass of weeds, ice, etc., floating on the surface of water.

A scum formed on wine (beer, etc.) during fermentation. Also: the algal bloom which forms on pools of stagnant water. Cf. mantle, v. 6. Obsolete.

Supernatant liquid.

The slimy scum rising to the surface of salt-pans. Obsolete.