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

• Lexulous
• Wordscraper
• Wordosaur

ad. In a gullible way or manner.

"And I say this as someone who read Germs, her book on bio weapons, and (gullibly) believed every word of it, but then found out it was all a fraud after the IraqWar."