трудный

difficilis [e];
arduus [a, um];
asper [a, um];
laboriosus [a, um];
impeditus [a, um];
involutus [a, um];
impotunus [a, um] (pauperies);
iniquus [a, um] (tempus;
locus;
via);
+ трудный вопрос ardua quaestio (alicui solvenda est);