Limestone
Lime´stone` Pronunciation: līm´stōn`
| n. | 1. | A rock consisting chiefly of calcium carbonate or carbonate of lime. It sometimes contains also magnesium carbonate, and is then called magnesian or dolomitic limestone. Crystalline limestone is called marble. |
| Noun | 1. |  limestone - a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals |