ADK
additional decryption key

ADL

Anti-Defamation League

it's a real thing

ADM

Archer Daniels Midland

...

ADN

ADO

Ancient Defamation Order (which does not exist)

ADP

they're a payroll company

ADQ
A DQ down the street :D

ADR

A Daring Rescue

ADS

I hate 'em! I block them!

ADT

they're a security company

ADU
Short for adult in the book section

ADV

adverb or advanced

ADW

A Double Whopper

ADX
>.>
<.<

ADY

ADZ
so many adz on other sites....