unwitty

Someone who tries to be witty, but fails.

He was so unwitty when he text messaged me this...
"So far I just want u to know that ur one of the most beautiful women i have ever met both inside and out. One could say 'girl ur the shit' Have a great day!"

Unwittyful

Another and better way to say unintelligent/Dim

Andy that was unwittyful of you to say that!