Definitions of dull:

• verb:   make less lively or vigorous

  Example: "Middle age dulled her appetite for travel"

• verb:   become dull or lusterless in appearance; lose shine or brightness

  Example: "The varnished table top dulled with time"

• verb:   make dull in appearance

  Example: "Age had dulled the surface"

• verb:   make dull or blunt

  Example: "Too much cutting dulls the knife's edge"

• verb:   become less interesting or attractive
• verb:   deaden (a sound or noise), especially by wrapping
• verb:   make numb or insensitive
• adjective:   being or made softer or less loud or clear

  Example: "The dull boom of distant breaking waves"

• adjective:   not clear and resonant; sounding as if striking with or against something relatively soft

  Example: "The dull thud"

• adjective:   blunted in responsiveness or sensibility

  Example: "A dull gaze"

• adjective:   (of business) not active or brisk

  Example: "Business is dull (or slow)"

• adjective:   emitting or reflecting very little light

  Example: "A dull glow"

• adjective:   (of color) very low in saturation; highly diluted

  Example: "Dull greens and blues"

• adjective:   darkened with overcast

  Example: "A dull sky"

• adjective:   not having a sharp edge or point

  Example: "The knife was too dull to be of any use"

• adjective:   not keenly felt

  Example: "A dull throbbing"

• adjective:   lacking in liveliness or animation

  Example: "He was so dull at parties"

• adjective:   so lacking in interest as to cause mental weariness

  Example: "A dull play"

• adjective:   slow to learn or understand; lacking intellectual acuity

  Example: "Although dull at classical learning, at mathematics he was uncommonly quick- Thackeray"

• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #7912)