(NOT BRIGHT) [adjective] -er, -est - not clear, bright or shiny; darkIf your cat's coat is dull, feed it Catto cat food!We could just see a dull glow given off by the fire's last embers.The first day of our holiday was dull (= cloudy).
DULL
Meaning of DULL in English
Cambridge English vocab. Кембриджский английский словарь. 2012