A melonmare is a nightmare brought on by a melon.
Undoubtedly I am not the first person to have experienced a melonmare, but perhaps I am the first person to have coined the word?
My melonmare happened on the night of 26th May 2003. My girlfriend and I ate half of a melon each before going to bed, and both woke up a couple of hours later with a sore throat and having had disturbing nightmares. By morning all effects of the melon had worn off and we resumed our normal lives*...
Seb Wills, 27th May 2003
*Or perhaps not -- do normal people write web pages like this one?