If something is ascending, it's rising or moving up. At a hot air balloon race, you'll see dozens of ascending balloons.
An ascending road appears to rise in front of you as it curves up over a hill, and an ascending bird flies up into the sky. To ascend is to rise, and the adjective ascending describes a rising or growing thing. You can also use it figuratively: "She's an ascending queen, rising to the throne after the death of her father." In Latin, ascendere, "to climb up," and also "to rise" or "to reach."