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.
Foam or froth of liquid, particularly that of seawater.
To froth.