dull

Not bright or shiny; lacking lustre or vividness.

"The old silver had a dull sheen."

Lacking interest or excitement; boring and uninspiring.

"The lecture was incredibly dull."

To make or become less bright, sharp, or interesting.

"The rain dulled the colours."

Of a pain, not sharp or intense but persistent.

"She felt a dull ache in her back."

Not sharp or pointed; blunt.

"The knife was too dull to cut."