1 a small stick of this rock used for writing -- gesso
2 If two people are like chalk and cheese, they are completely different from each other -- essere del tutto diversi, essere come il giorno e la notte
3 to write something with a piece of chalk -- scrivere con il gesso
5 (a piece of) a chalk-like substance used for writing (especially on blackboards) -- gessetto
a box of chalks.