Even if you feel the applicant has been rude, make the offer withdrawal official by sending a letter. There may be extenuating circumstances and the letter is one last chance for the applicant to respond.
1234, Main Street
Boston, MA 02123
<Recipient Address Goes Here>
Since we did not hear from you in response to our job offer, I regret that we must now withdraw that offer. We were impressed with your qualifications but can no longer wait for your response and must fill the position with another candidate.
We're disappointed that you won't be joining Abc Company and wish you well in your future endeavors.
encl: <List of enclosed items goes here>