abstruse
UK /əbˈstruːs/ US /æbˈstrus/ Syllables: ab-struse
Quick answer
Difficult to understand because it's so complex or obscure.
Abstruse describes an idea, a theory or a piece of writing that is hard to understand because it is deep, complex or very specialized. An abstruse argument is not just difficult. It is difficult because it deals with obscure or technical things that most people do not know. Close words are obscure, arcane, esoteric, recondite, cryptic and incomprehensible. The opposite is clear, obvious, simple or understandable. Abstruse is formal and is often used for philosophy, mathematics, law and theology. It can sound a little critical when used about writing that could have been plainer. The adverb is abstrusely and the noun is abstruseness. Do not confuse it with obtuse, which means slow to understand, or with abstract.
"The professor's lecture on quantum theory was too abstruse for most first-year students."Meanings
- Difficult to understand because it is complex, deep or specialized.
- Hidden or secret (obsolete).
Example sentences
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"The professor gave an abstruse lecture on number theory."
Level C1, Meaning 1
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"He found the legal language abstruse."
Level C1, Meaning 1
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"The book is full of abstruse arguments about language."
Level C1, Meaning 1
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"Her abstruse reasoning left the class confused."
Level C1, Meaning 1
Synonyms and antonyms
Look-alikes and common mistakes
- obtuse : Obtuse means slow to understand, or not sharp. Abstruse describes the idea that is hard to understand.
- abstract : Abstract means existing as an idea, not as a physical thing. Abstruse means hard to understand.
- obscure : Obscure means not well known or not clear. Abstruse things are obscure because they are deep or technical.
Word family and forms
Forms: more abstruse, most abstruse
Word partners
Words and phrases that often go with "abstruse".
- abstruse theory
- abstruse argument
- abstruse concepts
- abstruse language
- abstruse mathematics
- abstruse philosophy
- abstruse details
Origin
Abstruse came into English in the late 1500s from the Latin word abstrusus, meaning thrust away or concealed. The Latin word is the past participle of abstrudere, built from abs, meaning away, and trudere, meaning to thrust or push. The older sense of hidden or secret is now obsolete, and today the word means hard to understand.
Checked against: Wiktionary, the free dictionary, Dictionary.com.
How to remember it
Abstruse comes from a Latin word meaning pushed away or hidden. An abstruse idea is pushed out of easy reach.
Test yourself
Which word fits the gap? "The professor gave an _____ lecture on number theory."
Answer: abstruse
In your own words, what does "abstruse" mean?
Difficult to understand because it's so complex or obscure.
Learn next at C1
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Sources and credits
- Wiktionary, the free dictionary (CC BY-SA 4.0) · used for the origin, meanings, pronunciation · checked Nov 2, 2026
- Dictionary.com · used for the origin, meanings, word family · checked Nov 2, 2026
- Cambridge Dictionary · used for the meanings, pronunciation · checked Nov 2, 2026
Last reviewed November 2, 2026. Report a mistake on this page