Note: You can add a term as a plain Keyword match or as a Regex pattern for more advanced matching.
STEP ONE
Go to Policy > Block List, then select the Search Terms tab.
Search Terms tab under Block List
STEP TWO
Choose a Type (Keyword or Regex), then enter your term(s) in the Keywords box.
Enter the term(s) to block in the Keywords field
STEP THREE
Click Add Search Term to save it. The new term appears in the list below with its type.
Add Search Term button
STEP FOUR
To remove a term later, click the trash icon next to it in the Actions column.
Delete a saved search term via the trash icon
Related: How to Block a Category · How to Block a Website