mac·ro·seism \ˈmakrōˌsīzəm sometimes -sez- or -sāz- or -sēz-\noun Etymology: International Scientific Vocabulary macr- + -seism : a severe or major earthquake — compare microseism • mac·ro·seis·mic\|makrō|sī]zmik also ]sm- sometimes -|se] or -|sā] or -|sē]\adjective