[BwanaNdege]

Well, “technically”,:

“Inertia: tendency of an object to resist changes in its velocity.”

http://www.physicsclassroom.com/class/newtlaws/u2l1c.cfm#state

[Hacklehead]

It’s been a long time since I took physics but as I remember it inertia was the tendency of a body at rest to stay at rest.

[GOP_Party_Animal]

"Inertia" in the sense of linear motion, is the layman's term of how an object resists changes in motion. But it's not really correct because there is no way to calculate inertia. What's the formula for linear inertia? What are its units? It you read through the physics page you posted, and thinking about how far the cannonball moved despite barriers, you'll find that they are actually talking about momentum: Momentum = mass * velocity. Or when they're talking about the resistance to a change in linear motion, they're simply talking about mass.