Treadmill

From WoWWiki

Also the "Leveling Treadmill".

When an MMORPG has large experience point requirments for each level (usually to keep players playing and paying), playing is said to feel like running a on a treadmill. You spend a lot of time killing before you see any progress in levels.

World of warcraft has less of of a treadmill feel than a lot of other MMORPGs, though it is still there, as characters can take a few weeks to months to level, depending on how long the person plays and how much the person uses Powerleveling strategies.

See also Grinding.