Sinus Meridianii

[see-nuh s muh-rid-ee-ah-nee-ee, sahy-nuh s muh-rid-ee-ey-nee-ahy]

noun

an area on the equator of Mars, appearing as a dark region when viewed telescopically from the earth.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019