The Collaborative International Dictionary
Decreasing \De*creas"ing\, a. Becoming less and less; diminishing. -- De*creas"ing*ly, adv.
Decreasing series (Math.), a series in which each term is numerically smaller than the preceding term.
Wiktionary
adv. In a decreasing manner.
Usage examples of "decreasingly".
In fact, by now, though his conscience still bothered him, and would continue to bother him decreasingly for some time, David was thankful that he had accepted Karl's advice and not taken responsibility for the accident.
Also, although Ted Cole’s books for children were still widely read, Ted himself (at seventy-seven) was decreasingly famous—at least in the Hamptons.
Somewhere along the coast in the other direction, men were burrowing beneath the Forth, scooping out coal in a decreasingly profitable curve.
The division in the two tubes that resulted was very plain: the centre tube was white in colour, while the tube that surrounded it was decreasingly green as it approached the inner wall.
He’d abandoned his medical practice, his license was suspended, and he’d gone through a series of decreasingly productive jobs.