nonsensical

• nonsensic (very rare)
• non-sensical

From nonsense + -ical.

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nonsensical (comparative more nonsensical, superlative most nonsensical)

1. Without sense; absurd.

   Synonyms: meaningless, unmeaning, absurd, foolish, irrational, preposterous

   Antonyms: comprehensible, commonsensical, logical, rational, sensible, sensical

   • 1837, L[etitia] E[lizabeth] L[andon], “Prudence in Politics”, in Ethel Churchill: Or, The Two Brides. […], volume II, London: Henry Colburn, […], →OCLC, page 179:

     Well, her very foolish grandmother has mixed herself up in some nonsensical correspondence with the court of St. Germains; or, rather, has let herself be made a tool by Mr. Trevanion, who, I am happy to say, is not Ethel's husband; they arrested him just in time.

   • 2025 June 7, Paul Rosenzweig, “The Biden Investigation Is a Path to Even Greater Lawlessness”, in The Atlantic‎^[1], archived from the original on 7 June 2025:

     President Donald Trump’s presidential memorandum ordering an investigation of Joe Biden’s cognitive decline and his use of the autopen […] is also nonsensical fan service, amplifying addled MAGA conspiracy theories that contend, with a straight face, that Biden was really a robotic clone.

   • 2025 June 17, Arwa Mahdawi, “What SJP’s selfie trick tells us about the terrifying rise of conspiracy theories”, in The Guardian‎^[2], →ISSN:

     Conspiracy theories have become so mainstream that they are even prompting nonsensical legislation. Earlier this month, Louisiana lawmakers sent a bill to the state’s governor seeking to ban “chemtrails” – which don’t actually exist.

• The form non-sensical is much less common while nonsensic is extremely rare.^[1]
• Webster 1828 defined this as "Unmeaning; absurd; foolish." Webster 1913 defined this as "Without sense; unmeaning; absurd; foolish; irrational; preposterous."

• “nonsensical”, in OneLook Dictionary Search.
• “nonsensical”, in The American Heritage Dictionary of the English Language, 5th edition, Boston, Mass.: Houghton Mifflin Harcourt, 2016, →ISBN.
• “nonsensical”, in Collins English Dictionary, 2011–present.
• “nonsensical” (US) / “nonsensical” (UK) in Macmillan English Dictionary.