I've seen this term thrown around facebook in the past few days, largely by folks who misunderstand how the term is used. It does NOT mean a Witch who drank too much around the fire after a ritual. That's just a regular hangover ;)
A Witch's Hangover is when one is energetically depleted after intense ritual, spell work or other craft related operations which require vast amounts of metaphysical energy. Did you lead a circle wherein no one sustained the energy except for you? Did you take on a particularly energy intensive part in a ritual or spellcasting? Did you engage in trance or prophecy? Did you raise a lot of energy with the group? Were you the focus for the energy? You might suffer from a Witch's Hangover the next day.
What does it feel like? For me, it's like an actual hangover: I feel very sluggish, retain water, dry mouth and throat, headache and general signs of dehydration.
What do I do? Same thing for a hangover: I drink a LOT of water. B vitamins help me too! I find myself craving potatoes after intense work, a very grounding food.
Around the time of the full moon, some Witches find themselves on what is referred to as The Wild Hunt. Sometimes you can astral travel or journey without advanced planning. When you wake up feeling more tired than when you went to sleep.... could be Witches Hangover!
It's not the same thing as having a headache from too much energy, or the moon affecting the tides of your body. It's certainly not about acting the fool or being a "lunatic" as we know it in the muggle sense of the term. It's the physical consequences of spending a great amount of magical energy.
Yet another analogy: Ever start exercising after you've been dormant for a while? Or have an intense workout despite a regular exercise routine? I'm kinda sore the next day. You too? The same thing is true when you're talking in terms of energy, both for the problem and the solution: You have to grow your magical muscles. Doing that starts with a foundation of daily practice including (at least for me) ritual, meditation, and offerings. The more work you do with energy and with spirit, the stronger you get, the more you can do, and the less likely it is you will suffer a magical hangover.
But wow that last one was a doozy. After Saturday's Nemoralia celebration I was seriously hung over on both Sunday and some of Monday. It was only this morning that I realized where my bumps and bruises are because the general feeling of walking through cotton had finally lifted!
What can I say- when we magically party, we party hard!
I am not recommending the product in the picture, I just think the name is hillarious! And Appropriate!