Difficult to understand, hard to grasp mentally, deep, profound, incomprehensible, unfathomable.
→ Antonyms of abstruse include manifest, discernible (word 32 of Level 3), lucid (word 45 of Level 3), and perspicuous, which I’ll discuss later in this level.
Challenging synonyms of abstruse include inscrutable (word 48 of Level 3), esoteric (word 29 of Level 5), and also occult, cryptic, enigmatic, arcane, recondite, and acroamatic.
Let’s take a closer look at some of those rather abstruse synonyms, all of which apply to things that are secret and mysterious or difficult to understand.
By derivation esoteric (ES-uh-TER-ik) means understood by a select group, intended only for the knowledge of a few; hence, secret, confidential, or beyond most people’s knowledge or understanding.
Occult (uh-KUHLT, first syllable like a in ago) by derivation means hidden or concealed. Today occult may be used either of that which is secret because it is hidden from view or of that which is secret because it is mysterious or incomprehensible.
Cryptic (KRIP-tik) comes from the Greek kryptos, hidden, which comes in turn from the verb kryptein, to hide. The familiar word crypt comes from the same source and means a burial chamber hidden underground. In modern usage cryptic applies to that which has a hidden meaning: cryptic ideas are mystifying ideas; a cryptic message is an incomprehensible or coded message.
The noun enigma (i-NIG-muh) and the adjective enigmatic (ENig-MAT-ik) come from a Greek verb meaning “to speak in riddles.” An enigma is something or someone like a riddle, a mystery, puzzle. Enigmatic means like an enigma, and therefore perplexing, puzzling, ambiguous, or incomprehensible. Enigmatic is perhaps most often used of something written or stated, but the word may also apply to actions and to people.
Arcane (ahr-KAYN) comes from the Latin arcana, meaning “shut, closed,” or “secret,” and ultimately from arca, a box or chest, especially a money chest. By derivation arcane means shut or closed up, and, like esoteric, arcane is now used of that which is known only to a few people. The word usually applies to knowledge or information, as an arcane theory.
Recondite (REK-un-dyt) comes from the Latin recondere, to put away, conceal. In modern usage recondite applies to that which is beyond the grasp of the ordinary person. To most people, for example, particle physics is a recondite subject.
Acroamatic (AK-roh-uh-MAT-ik) is an abstruse and unusual synonym of esoteric—so unusual that you won’t find it listed in most dictionaries. Historically, acroamatic applies to certain writings by the ancient Greek philosopher Aristotle (AR-iSTAHT-’l) that were addressed to his disciples as opposed to his exoteric (EKS-uh-TER-ik) writings, which were intended for a popular audience. Acroamatic comes from the Greek akroamatikos, which means “designed for hearing only.” According to the encyclopedic Century Dictionary (1914), Artistotle’s acroamatic writings “were addressed to ‘hearers,’ that is, were intended to be read to his disciples or were notes written down after his lectures.” In a general sense, acroamatic may refer to that which is esoteric, intended for and understood by a select group, recondite, beyond the grasp of the average person, and abstruse, extremely hard to understand.
By derivation abstruse means put or pushed away, and today the word connotes that which has been pushed out of the realm of comprehension. Scholars and scientists are fond of using abstruse academic jargon to discuss abstruse subjects and ideas. If you buy a computer, the user’s manual probably will be so abstruse that you’ll wind up having to call the customer service hotline for help.