abstruse
adj.
1590s, from Middle French abstrus (16c.) or directly from Latin abstrusus "hidden, concealed, secret," past participle of abstrudere "conceal," literally "to thrust away," from ab- "away" (see ab-) + trudere "to thrust, push" (see extrusion). Related: Abstrusely; abstruseness.
〔李〕[abs-;trus;-e] a.难解的，深奥的 ←trud,trus (L trudere,trusum)=to thrust 刺