Webster's Revised Unabridged Dictionary (1913 + 1828)
result(s) from the 1913
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
2. Remote from apprehension; difficult to be comprehended or understood; recondite; as, abstruse learning.
Profound and abstruse topics.