To
fly not under one's own power but by
harnessing and riding
thermals, that is,
columns of
hot air rising.
Also a description for the primary mode of transportation followed by slugs and snails, as they slip around on their little trails of self-secreted mucous. That a word typically used to describe such a graceful act is applied to these foul and unwholesome beings simply clinches the fact that they are abomination and must be stomped out.