That build up of sweaty white stuff around the saddle of a racehorse.
It was hot at the races yesterday. All the horses had saddle froth.
The white frothy secretions between a womans legs after a sustained, sex session. This is not too dissimilar the white sweaty stuff under and around a horses saddle on a hot day.
i was smashing this bird for hours the other day. Jesus, my nuts were covered in saddle froth.