Meaning

• Unable to speak; lacking power of speech (kept in "deaf, dumb, and blind").

  "His younger brother was born dumb, and communicated with sign language."

• Silent; unaccompanied by words.

  "dumb show"

• (especially of a person) Extremely stupid.

  "You are so dumb! You don't even know how to make toast!"

• Pointless, foolish, lacking intellectual content or value.

  "Brendan had the dumb job of moving boxes from one conveyor belt to another."

• Lacking brightness or clearness, as a colour.