Assuming that "all the way west of the Prime Meridian" would be on the opposite side of the globe from the prime meridian, or at 180o, "halfway west of the Prime Meridian" would be the 90oW meridian.
According to the Wikipedia article on 45X90 points, it would be longitude 90 degrees 0 minutes 0 seconds East.
This is 90 degrees east longitude, and has no special name.
Located bear this line is the city of Thimphu, capital of Bhutan.
The 180th Meridian or 180° longitude is the exact opposite of the Prime Meridian.
The longitude of every point on Earth, from the Prime Meridian out to halfway around the world in the westerly direction is labeled "west longitude". The longitude of every point on Earth from the Prime Meridian out to halfway around the world in the easterly direction is labeled "east longitude".
Halfway between the Prime Meridian and 80 degrees west has to be pretty close to 40 degrees west, we'd say.
The Prime Meridian is at zero degrees longitude and every possible latitude.
180° is halfway around a circle or a sphere. Beginning at the Prime Meridian, you can travel EITHER east OR west, and after you have traveled 180 degrees, you'll arrive at the same line either way ... the meridian of 180° E and W longitude, which is halfway around the Earth in either direction from the Prime Meridian.
90 degrees west
The line 90 degrees west longitude, which includes the cities of New Orleans LA and Memphis TN.
The longitude of such a place is 90° West. On any randomly chosen map or globe, there may or may not be a line printed to show that longitude.
The Prime Meridian is zero degrees longitude.
0 degree longitude is is called the Prime Meridian.
The 180th Meridian or 180° longitude is the exact opposite of the Prime Meridian.
90 degrees west longitude
The longitude of every point on Earth, from the Prime Meridian out to halfway around the world in the westerly direction is labeled "west longitude". The longitude of every point on Earth from the Prime Meridian out to halfway around the world in the easterly direction is labeled "east longitude".
90 degrees
Halfway between the Prime Meridian and 80 degrees west has to be pretty close to 40 degrees west, we'd say.
The Prime Meridian is at zero degrees longitude and every possible latitude.
180° is halfway around a circle or a sphere. Beginning at the Prime Meridian, you can travel EITHER east OR west, and after you have traveled 180 degrees, you'll arrive at the same line either way ... the meridian of 180° E and W longitude, which is halfway around the Earth in either direction from the Prime Meridian.