What is Dull ?
Dull is (adj) 1. not exciting, not interesting The story is rather dull. What’s so interesting about old churches? I find them dull. 2. (of weather.) grey and miserable a dull cloudy day 3. (of colours) not bright They painted the sitting room a dull green. (NOTE: duller dullest)
source: Easier English, Student Dictionary Upper Intermediate Level