What does 字 mean?
字 is a Japanese noun meaning “letter; character” in English. It can also be translated as “handwriting, the ... word (e.g. "the L word" = "love")” depending on context. It is written as 字 in kanji, じ in hiragana, and ji in romaji. This word is part of JLPT N4 vocabulary.
Example sentence
君は字がうまいね。
You write very neatly, don't you?