Graffiti
Scribble, Sketch
noun, verbal noun
When writing just happens to "fall" on the wall (whoops, wasn't me who did that, how strannnnge) it's writing that's not supposed to be where it is. This kind of writing is graffiti.
This is a jukugo word, which usually means on'yomi readings from the kanji. 書, however, is kun'yomi in this case and also has rendaku. So just remember that it's read as が for this vocab and you'll be fine.
コウイチの落書きは今やオークションで百万ドルで落札されるまでになった。
Koichi's sketches have increased in value by as much as a million dollars at auctions.
新宿駅の地下道には、昔、たくさんの落書きがしてありましたが、今はほとんど見当たりません。
There used to be lot of graffiti along the underground passages at Shinjuku Station a long time ago, but we rarely see them now.
スプレーでの落書きアートは既に少し時代遅れです。新しい芸術家達は、壁の汚れをゴシゴシ擦って洗い落としながらアートを創りだします。
Spray-painting graffiti is already a bit old-fashioned. The newer artists create works of art by scrubbing the dirt off the wall.