difficult - a) needing much effort or skill; b) troublesome, perplexing; c) (of a person) a not easy to please or satisfy; d) characterised by hardships or problems (a difficult period in on's life).

a trouble - a) a misfortune; calamity; mishap; b) a distressing or difficult happening or situation.

(rhet.) a style that is complex to understand (considered as a fault in literary work).