A conjunction of the words "dick" and "rectum". Although it supposedly means an order or decree, it actually is a discreet insult used when insulting someone of a lower IQ than yourself.
Thinking that "Tums" (An antacid is any substance that counteracts stomach acidity) are a highly dangerous and highly addictive drug. Knows side effects of being a dictum are the grating of cherry flavored Tums and snorting them through the nose. Most people also consider these people unworthy of being called intellectuals and therefore pronounced "dicks" instead.
Dick + Tum = Dictum
Little did Timmy Gonzales' mother know but her willingness to expose her son to Tums lead to a habit that later expanded into a form of addiction leading to a complete collapse of his social life and the permanent title of dictum.
"I wonder if Timmy's girlfriend knows what a dictum he is"
A text from a male (usually one who is intoxicated, the ex-boyfriend of the recipient, or who wants to have sex with the recipient) in which the main content is a picture of the male's penis.