A word very valuable in situations where you are playing Scrabble and wish to temporarily infuriate your opponent with your apprent complete disregard for the simple dictionary-based rules of the game, only to have them remark in your favour with a certain astonishment when they discover it really is a word.

A pubic hair piece. A toupee for the pubic area/genitals. In the 1700’s when mercury was used to treat sexually transmitted diseases (Gonorrhea or Syphilis) one of the side effects was the loss of pubic hair. To disguise this condition, that was not cured by mercury, a Merkin was employed.

The near perfect linear alignment of 3 or more celestial bodies (as in the sun the moon and the earth during a solar eclipse) in a gravatational system.

A lesbian orgy.

In astronomy, syzygy is the alignment of three celestial bodies.