"Block markup" is a term used in the sources of PmWiki indicating all markups resulting in HTML block elments^[1] or in other words multiple paragraphs and other content.

• Forms
• paragraphs
• indent/outdent
• lists
• list items
• headings
• divisions
• images
• pre
• tables

WikiStyles can be applied to blocks, else you don't need to bother about "blockmarkup" as a PmWiki user.