Glossary
Ult economy
In one line: Keeping track of your ultimates and the enemy's, and deciding when to use them, the way you manage money.
What it means
Ultimates charge with points: one for each kill, each death, each orb picked up on the map, and for planting or defusing the spike. Each ultimate needs a different number of points.
Managing ultimates is like managing money: an ultimate is a resource. You know which ultimates the enemy has (the scoreboard shows it) and play around them; you line up your own for an important round instead of using them randomly; you do not burn an ultimate in a round that is already won or already lost.
An example
The scoreboard shows their controller has their ultimate ready. You know it can lock down a whole site: instead of attacking where they can use it best, you go to the site furthest from them and force a worse use of it.