i-adjective
hard to come out; difficult to occur; unlikely to happen
Describes something that does not emerge, appear, or happen easily. Often used for physical emergence, occurrence of events, or expression of feelings.
このドアは古くて開けにくいし、音も出にくい。
This door is old and hard to open, and it doesn't make sound easily either.
彼は人前では言葉が出にくい。
He has difficulty getting words out in front of people.
Antonym: easy to come out, likely to occur.
Similar meaning but づらい emphasizes emotional or psychological difficulty, while にくい is more objective.
Compound of 出 (de, 'come out') + にくい (nikui, 'difficult to do'). The auxiliary adjective にくい attaches to the masu-stem of verbs to express objective difficulty.