abstruse

Etymology

PIE word *h₂epó Learned borrowing from Latin abstrūsus (“concealed, hidden; having been concealed”), an adjective use of the perfect passive participle of abstrūdō (“to conceal, hide; to push or thrust away”), from abs- (from ab- (prefix meaning ‘away; from; away from’)) + trūdō (“to push, shove; to thrust”) (ultimately from Proto-Indo-European *trewd- (“to push; to thrust”)). cognates * Catalan abstrús * German abstrus (“abstruse”) * Italian astruso (“abstruse”) * Middle French abstruse (modern French abstrus, abstruse (“(derogatory, literary) abstruse”) * Portuguese abstruso (“abstruse”) * Spanish abstruso (“abstruse”)

adj

1. Difficult to comprehend or understand; obscure.
   Some time the good makithe an ile end⸝ ãd the ile a godd. In this opiniõ⸝ and in ſcrutable miſterie be werithe all his wittes⸝ and at the end of his cogitacions⸝ fyndithe more abſtruſe⸝ and doutfull obiections thẽ at the beginning⸝ […] Sometimes the good maketh an ill end, and the ill a good. In this opinion, and inscrutable mystery be weary all his wits, and at the end of his cogitations, findeth more abstruse, and doubtfull objections than at the beginning, […] [1548], Joanne Hopper [i.e., John Hooper], “Curiositie”, in A Declaration of the Ten Holy Cõmaundementes of Allmygthye God[…], [Zurich: Christoph Froschauer], →OCLC, page CCXVIII
   A second rescript followed, commanding all bishops not merely to subscribe the dominant opinions on these profound and abstruse topics, but to condemn their authors, Pelagius and Cœlestius, as irreclaimable heretics, and this under pain of deprivation and banishment. 1854, Henry Hart Milman, “Pelagianism”, in History of Latin Christianity;[…], volume I, London: John Murray,[…], →OCLC, book II, page 127
2. (obsolete) Concealed or hidden; secret.