To stop the breathing of
The air of the chamber stilled and grew heavy, as if it meant to suffocate him.
The fire element will quickly suffocate under the demand of an earth sign.
Other contaminants, like grease from industrial food processing, may leech the oxygen out of the water and suffocate fish.
To actually kill them, you may need to leave the shampoo on your dog for several minutes to suffocate the fleas.
This might seem as it would be a lot of fun, but the weight of it could cause someone to suffocate.