His lecture was ____, or boring.

adjective

1. Tedious, uninteresting

   "dull lectures"

2. Lacking sharpness of edge or point

   "a dull knife"

3. Not resonant or ringing

   "a dull booming sound"

4. Lacking in force, intensity, or sharpness

   "a dull ache"

5. Lacking brilliance or luster

   "a dull finish"

6. Cloudy

   "dull weather"

7. Low in saturation see saturation and low in lightness

   "a dull green"

8. Mentally slow stupid
9. Slow in perception or sensibility insensible

   "somewhat dull of hearing"

10. Lacking zest see zest or vivacity listless

    "a dull performance"

11. Slow in action sluggish

    "dull markets"

verb

1. To make dull

   "dull a knife's edge"

2. To become dull

   "The blade dulled with use."

adjective

1. Mentally slow dim-witted

   "He tried to teach her how to pronounce his last name with a French twirl, and when her tongue could not master it he accused her of being dull-witted."

idiom

1. Very boring or dull

   "The conversation was as dull as dishwater."

idiom

1. Very boring

   "The book is as dull as ditchwater."

idiom

1. Never a time when something exciting is not going on always something exciting happening

   "There's never a dull moment in our house."