Periodt, pronounce as pɪərɪədt or peh-ri-od-t is a popular slang that widely use on the internet. By definition Periodt used when you said something true without a doubt and having nothing else to say on that topic.
Periodt! That's final. Periodt or Period't, is not a typo. The letter "t" at the end of the word is used to impersonate certain speech accents, more accurately, African American accents. Periodt usually being used by black online communities, the word frequently used to end any discussion.
When someone said "Periodt!", there is nothing else to be added. There is no more to be said. You can't debate anymore. The conversation is over. No more discussion. For instance, "Black History Month Periodt!" or "my twitter account, my rules. periodt."