Webster's Revised Unabridged Dictionary · 1913

Megameter

Megameter , noun

[Mega- + -meter: compare French mégamètre.]

1.
(Physics) An instrument for determining longitude by observation of the stars.
2.
A micrometer. [Rare & Obsolete] — Knight

Megameter , noun

[Mega- + meter, metre, n., 2.]

In the metric system, one million meters, or one thousand kilometers.

Also: Megametre