The process by which air is circulated through or mixed with a substance such as soil or a liquid.
By extension, a process in which other gases (such as carbon dioxide or nitrogen or argon) are circulated through or mixed with a substance (usually liquid), sometimes with the consequence of increasing the transfer of air into the same liquid at the surface due to the induced circulation.
Lather; foam or froth formed by mixing soap and water.
Beer.
To cover with, or as if with, soapsuds.