asphyxiate
verb.
deprive of oxygen and prevent from breathing
Othello smothered Desdemona with a pillow|The child suffocated herself with a plastic bag that the parents had left on the floor
Synonym: smother, suffocate
verb.
impair the respiration of or obstruct the air passage of
The foul air was slowly suffocating the children
verb.
be asphyxiated; die from lack of oxygen
The child suffocated under the pillow
Synonym: stifle, suffocate