Not determinate; unsettled or uncertain(adjective)
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Use "undeterminate" in a sentence
"Rock and Mack, both squirrel feists of undeterminate lineage."
"And that cannot but be very far from a positive complete idea, wherein the greatest part of what I would comprehend is left out, under the undeterminate intimation of being still greater."
"For in duration we consider it as if this line of number were extended both ways — to an unconceivable, undeterminate, and infinite length; which is evident to any one that will but reflect on what consideration he hath of Eternity; which, I suppose, will find to be nothing else but the turning this infinity of number both ways, a parte ante, and a parte post, as they speak."