Dull

banal

(boring, not exciting or interesting — see also boring)

bont

(lacking the ability to cut easily; not sharp)

mat

(not shiny)

obtuz

(not bright or intelligent)

plictisitor

(boring, not exciting or interesting — see also boring)

tocit

(lacking the ability to cut easily; not sharp)

toci

(to render dull)

toci

(to become dull)