[sahy-zuh
m, -suhm] 
| an earthquake. |
| earth·quake (ûrth'kwāk') n. A sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity. Also called seism, temblor. |
| seism (sī'zəm) n. See earthquake. [Greek seismos, from seiein, to shake.] |