This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. That may be modified by the addition of a suffix

adj. Taking the role of a suffix

Of or pertaining to a suffix; of the nature of a suffix.

"A: “Who all,” like “you all,” is a common redundant suffixal colloquialism and may be used without disadvantage in all but the most snobbish circles, even though it is not standard English."