What is an antomnym of dull?

An antonym of "dull" depends on the context in which you're using the word. Here are some possibilities:

If "dull" means lacking in excitement or interest:

* Exciting

* Stimulating

* Engaging

* Lively

* Thrilling

* Vibrant

* Spirited

If "dull" means lacking in sharpness or brightness:

* Sharp

* Bright

* Shiny

* Brilliant

* Gleaming

If "dull" means lacking in intelligence or wit:

* Sharp

* Clever

* Intelligent

* Witty

* Astute

If "dull" means lacking in sound or color:

* Loud

* Colorful

* Vibrant

* Rich

To choose the best antonym, consider the specific meaning of "dull" in your sentence.