It's when you've been planning trip out on the the RIB for weeks, and the forecast is perfect, plans are made, preparations complete - and then you wake up in the morning, and it's blowing a F8 and it's crap.
You go and kick the cat, the dog, and anything else you can get your foot anywhere near.
Now THAT is a Foul Weather Strop.
(D'Oh - Stephen beat me to it!!)