mad money: (noun) Money saved by a woman against the time when she wants to make an impulsive or therapeutic purchase.
It is not your
nest egg, float (reserve cash required to keep you from sinking), or
cushion (aka safety net or rainy day fund)
After paying all your obligated expenses, and whatever you need to towards your nest egg and/or cushion, and factoring in your normal required amount of pocket cash, you deposit a small amount of whatever is leftover into this mad money fund each week or month, for use when you want to buy that stuff you have been resisting, for when you can resist no more, or when you have an absolute emotional need to buy something for yourself to maintain your sanity.
If and when you purchase anything with this money, you do it for the sake of your own emotional and/or psychological well being, without any shame, guilt, or regret involved. It's ok to spend it frivolously. This money is usually never used to pay normal bills.
Traditionally, this is the cash your mom and/or grandmother probably kept hidden in a coffee can, that your dad and/or grandfather never knew about, made up from the cash leftover after doing the weekly grocery shopping (which is why they were fanatics about coupons), that she would occasionally use to buy herself nice things (new shoes, pretty dress, trip to a salon to have her hair done, etc.), anything she knew your dad/grandfather would say no to, but felt she needed for the sake of her own happiness.
If there was nothing in the coffee can, she knew she would have to wait till there was, before she could splurge on herself, again.
Currently, whatever I have in the way of donation credits is my mad money fund. Since it does take a little while to cash them out and make them available to spend on whatever, this in itself is kind of a deterrent not to spend them unless I really have to, to preserve my sanity. Since I don't currently have enough credits to spend on a shiny new more powerful pc, it makes frivolously buying one, very easy to resist.