The word "lithoid" refers to something that resembles or is related to rock or stone. Synonyms for lithoid include stony, rocky, petrous, and lapideous. These words all describe something with a hard, solid exterior that is similar to a rock. Other possible synonyms for lithoid could include mineral-like, granitic, earthen, or even fossilized. These words all convey the sense of hardness or durability that is associated with anything lithoid in nature. Whether describing a type of mineral or a geographical formation, using synonyms for lithoid can help to increase the precision and clarity of one's writing.