A soft landing in economics is a cyclical slowdown in growth that cools inflation or overheating without tipping into an outright recession. Central banks usually aim for one by raising interest rates enough to restrain demand, but not so aggressively that unemployment spikes and GDP turns negative.
The opposite is a hard landing, when policy tightening succeeds at lowering inflation only by causing a recession. Soft landings are hard to engineer because monetary policy works with long, uncertain lags.
Source: Soft Landing — Investopedia.