Balderdash

I'll go with #10, too.

1. The condition of having a forked tail.(jespah's wild idea poked Equus)
2. Lower back pain (Clary's ailment attacked jespah)
3. A hazy mist cloud most commonly found at densely populated urban areas. (najmelliw's- close-to-the-truth-but-no-takers bluff. Better luck next time, naj!)
4. Animal habit of sniffing other animal's backsides. (Equus, uh, nature to 'go to the dogs' offering bit Taffy)
5. A condition which effects a small population in which certain pressure against the coccyx stimulates erotic response. (littlek's sexual healing had no affect)
6. A phenomena that effects only people when they look to the skys on cloudy days but does not effect intellectual felines and canines. (Taffy Le Blanc animal instinct fooled no one)
7. A highly virulent strain of pathogenic bacteria (me! -dev- It's what it sounded like to me, and it fooled: P&L, littlek, and drom- THANK YOU!)
8. Perception of a Sentient subjective mind while viewing water-vapor shapes. (firstthought's not unlike the real answer held water with hiama)
9. Inner-cranial surgery (realjohnboy had no one wanting to be operated upon!)
10. Seeing pictures in the clouds (The REAL answer! Seen -in the stars?- by Clary, onyxelle, rjb and ft! *(AND Drom-!*Note correction.) Muy bueno! You all are just TOO smart!)
11. The mediaeval term for inflammation of the eyelids: blephartis. (drom-et-reve's old english disease was caught by naj)
12. A particularly nasty gram positive bacteria, producing nasty red weals and rashes on one's body (what hiama was dishin' out, nobody was takin!)
13. The muscle in the throat used to blow bubbles (Peace&Love floated this one in and Scarlettmarsden found it irresistible)

George knew that the original reference was "Cloud Cuckoo-land" from Aristophanes play "The Birds"
Good job, all. This was really fun. I'll try to work on the scoring tomorrow. Oy!

jolly good, though I think firstthought's definition is actually the same as number 10 so should attract 3 points! Not that I'm complaining