Answer:
An Anti-Meridian is a meridian opposite any given meridian of longitude.

Specifically the Anti-Meridian is the 180th meridian. That is the meridian opposite of the Prime Meridian.

The term Anti-Meridian is sometimes confused with Ante Meridiem.

Ante Meridiem is latin for before noon. Usually shown in English as "a.m.". Similarly, post meridiem, after noon, is shown in English as "p.m.".
Contributor: Stephen
First answer by Steve8rox. Last edit by Stephen Luce. Contributor trust: 5 [recommend contributor recommended]. Question popularity: 6 [recommend question].