Synonyms of the word

recondite

• adj. (of areas of study and literature) Difficult, obscure; particularly.
• adj. (as a general term, somewhat archaic ; as a term in botany and entomology, obscure, rare) Hidden or removed…
• adj. (zoology, rare) Shy, avoiding notice (particularly human notice).
• v. (obscure, rare, transitive) to hide, cover up, conceal.

abstruse

• adj. (obsolete) Concealed or hidden out of the way; secret.
• adj. Difficult to comprehend or understand; recondite; obscure; esoteric.

deep

• adj. (heading, of a physical distance) Extending far away from a point of reference, especially downwards.
• adj. (heading, intellectual, social) Complex, involved.
• adj. (sound, voice) Low in pitch.
• adj. (of a color) Dark and highly saturated.
• adj. (sleep) Sound, heavy (describing a state of sleep from which one is not easily awoken).
• adj. Immersed, submerged (in).
• adj. Muddy; boggy; sandy; said of roads.
• adv. Deeply.
• n. (literary, with "the") The deep part of a lake, sea, etc.
• n. (rare) A deep shade of colour.
• n. (US, rare) The profound part of a problem.
• n. (with "the") The sea, the ocean.
• n. (cricket) A fielding position near the boundary.

esoteric

• adj. intended for or likely to be understood by only a small number of people with a specialized knowledge…
• adj. Having to do with concepts that are highly theoretical and without obvious practical application; often…
• adj. Confidential; private.
• n. An esoteric doctrine or treatise; esoteric philosophy.
• n. One who believes, or is an initiate, in esoteric doctrines or rites.