Caliginous \kuh-LIJ-uh-nuhs\ , adjective;
1. Misty; dim; dark
According to Etymonline.com:
This word dates to the 1540's and comes from Latin caliginosus ("misty") which derives from caliginem (nominative caligo), meaning "mistiness, darkness, fog, gloom."
*Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Tuesday, December 21