Abstruse
Pronunciation : Ab*struse"
Part of Speech : a.
Etymology : [L. abstrusus, p. p. of abstrudere to thrust away, conceal; ab, abs + trudere to thrust; cf. F. abstrus. See Threat.]
Definition : 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 : Webster's Unabridged Dictionary, 1913