a. [ L. abstrusus, p. p. of abstrudere to thrust away, conceal; ab, abs + trudere to thrust; cf. F. abstrus. See Threat. ]
The eternal eye whose sight discerns
Abstrusest thoughts. Milton. [ 1913 Webster ]
Profound and abstruse topics. Milman. [ 1913 Webster ]
adv. In an abstruse manner. [ 1913 Webster ]
n. The quality of being abstruse; difficulty of apprehension. Boyle. [ 1913 Webster ]