laughing gas
noun/ˈlɑːfɪŋ ɡæs/
/ˈlæfɪŋ ɡæs/
[uncountable] (informal)- nitrous oxide (= a gas used especially in the past by dentists to prevent you from feeling pain)
Check pronunciation:
laughing gas
Definition of laughing gas noun from the Oxford Advanced Learner's Dictionary