Answer:

opaque

AnswerCrossword Clue
OPAQUEHard to see through
OPAQUEImpossible to see through
OPAQUEHard to grasp
OPAQUEUnclear
OPAQUELight-blocking
OPAQUENot easily understood
OPAQUEOpposite of transparent
OPAQUEHard to understand
OPAQUEMuddy