the product of a body's mass and its velocity
"the momentum of the particles was deduced from meteoritic velocities"
Of a body in motion: the tendency of a body to maintain its inertial motion; the product of its mass and velocity.
"The heavy truck possessed so much momentum that it was impossible to stop once it had started rolling downhill."
In plain English: Momentum is how much motion an object has based on its weight and speed, making it harder to stop once it's moving fast.
"The snowboarder gained momentum and zoomed down the hill without slowing down."
Usage: In everyday language, momentum refers to the strength or force behind an idea, trend, or action that makes it difficult to stop once started. Use this word when describing something gaining speed or influence rather than a physical object's specific mass times velocity calculation.
From Latin mōmentum. Doublet of moment and movement.