| source : web1913 | Abstruse \Ab*struse"\, a. [L. abstrusus, p. p. of abstrudere to thrust away, conceal; ab, abs + trudere to thrust; cf. F. abstrus. See {Threat}.] 1. Concealed or hidden out of the way. [Obs.] The eternal eye whose sight discerns Abstrusest thoughts. --Milton. 2. Remote from apprehension; difficult to be comprehended or understood; recondite; as, abstruse learning. Profound and abstruse topics. --Milman. | source : wn | abstruse adj : difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge; "the professor's lectures were so abstruse that students tended to avoid them"; "a deep metaphysical theory"; "some recondite problem in historiography" [syn: {deep}, {recondite}]