In Sitecore 9, am I able to assign a Pattern to a Contact? 

I think the answer is no. The system uses Patterns Cards to identify matches to Contacts. Additionally, from the Experience Profile, I do not see a way to manually assign a Pattern Card to a specific Contact.

While viewing a specific Contact in the Experience Profile dashboard, I was trying to find a way to assign a Pattern to a specific Contact. My intent is to override a Pattern that the system has assigned to a Contact.