— boring
— deadening
— deadly
— draggy
— dull
— earthbound
— ho-hum
— insipid
— irksome
— jejune
— mind-numbing
— narcotic
— pedestrian
— ponderous
— prosaic
— prosy
— putdownable
— slow
— soporiferous
— soporific
— tedious
— tiresome
— unamusing
— unexciting
— unstimulating
— wearisome