Simple past tense and past participle of misground.(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "misgrounded" in a sentence
"And this misgrounded Conceit of his, had like to have firmly rooted itself in his Mind, unless God had pursu'd him with his"
"Soon after he brought me a message from the King, that I should not expect this ceremony; but still upon the same misgrounded supposition, therefore unto this likewise I replied."