Something described as insuperable is impossible to gain control of, solve, or overcome.

// The book tells the inspiring story of a group of people who achieved a great deal despite nearly insuperable obstacles.

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"A love story comes into meteoric focus in this musical [The Lonely Few], which features a book by Rachel Bonds and a score by Zoe Sarnak. Two women who are attached to their cultural roots yet alienated by the conservative values of their communities hold for each other the answer to problems that until now have seemed insuperable." — Charles McNulty, The Los Angeles Times, 19 Mar. 2023

Insuperable is a super word: that is, it belongs to a family of English terms that come from the Latin word super, meaning "over." It first appeared in print in the 14th century, and as a close synonym of insurmountable, it still essentially means what it did then. Insuperable comes directly from the Latin word insuperabilis, which was formed by combining the negative prefix in- with the verb superare (which comes from super and means "to surmount, overcome, or excel") and the adjective abilis (meaning "able"). Hence, insuperabilis means "unable to be surmounted, overcome, or passed over," or more simply, "insurmountable." The word can describe physical barriers that cannot be scaled (such as walls or mountains) as well as more figurative obstacles.