Momentum \Mo*men"tum\, n.; pl. L. Momenta, F. Momentums. [L. See Moment.]

1. (Mech.) The quantity of motion in a moving body, being always proportioned to the quantity of matter multiplied into the velocity; impetus.

2. Essential element, or constituent element.

I shall state the several momenta of the distinction in separate propositions. --Sir W. Hamilton.

Source: Webster's Revised Unabridged Dictionary (1913)