i-adjective
hard to write; difficult to draw; doesn't write well
Covers both the difficulty of producing written characters or drawings, and the poor performance of a writing instrument.
このペンはインクがかすれて書きにくい。
This pen skips and is hard to write with.
細かい字は書きにくい。
Small characters are difficult to write.
Standard spelling using the auxiliary adjective にくい attached to the masu-stem of 書く.
Kanji spelling for にくい; less common but still seen.
Compound of the masu-stem of 書く (kaku, 'to write') + にくい (nikui, 'difficult to do').