Emily Dickinson Lexicon

AB-STRUSE, a. [L. abstrusus, from abstrudo, to thrust away, to conceal; abs and trudo; Ar. طَرَدَ tarada; Ch. טרו, to thrust; Syr. Sam. id.; Eng. to thrust.]

Hid; concealed; hence, remote from apprehension; difficult to be comprehended or understood; opposed to what is obvious. [Not used of material objects.] Metaphysics is an abstruse science. – Encyc.