asphyxiate

(verb) deprive of oxygen and prevent from breathing. Synonyms: smother, suffocate. Examples: "Othello smothered desdemona with a pillow." "The child suffocated herself with a plastic bag that the parents had left on the floor."

(verb) impair the respiration of or obstruct the air passage of. Synonyms: suffocate, stifle, choke. Example: "The foul air was slowly suffocating the children."

(verb) be asphyxiated; die from lack of oxygen. Synonyms: suffocate, stifle. Example: "The child suffocated under the pillow."