Downwarp
A downwarp can refer to any action that results in Mario's position being suddenly shifted downwards. A variety of tricks can lead to a downwarp.
Star Dance Downwarp
When in star dance, mario's position is constantly set of the referenced floor (the floor below him). Thus if he is in the air, he is downwarped to the floor below
Star/Pole Downwarp
If Mario collects a star while climbing a pole, he is instantly snapped to the floor below him. In most cases, such as the trees in [Bob-omb Battlefield], this only results in Mario being warped a small distance downward as the trees are near the ground to begin with. However, in Dire, Dire Docks, collecting a star while riding one of the moving poles can result in Mario being snapped to the floor under the water below him.
Cannonless
When doing the cannonless strat, Mario downwarps.
Platform moves out from under Mario
This causes the floor under Mario to not be the platform but possibly a floor more under the platform.
Squish Downwarp
Exposed Ceiling Downwarp
Grab Downwarp
Pedro spot Downwarp
Sliding (but not by using midair walk via double turnaround) while in a Pedro spot = Downwarp